U.S. patent application number 12/888820 was filed with the patent office on 2011-03-31 for method of producing photoelectric conversion element, photoelectric conversion element, and photoelectrochemical cell.
This patent application is currently assigned to FUJIFILM Corporation. Invention is credited to Keizo KIMURA, Katsumi KOBAYASHI, Yukio TANI.
Application Number | 20110076539 12/888820 |
Document ID | / |
Family ID | 43234271 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110076539 |
Kind Code |
A1 |
KOBAYASHI; Katsumi ; et
al. |
March 31, 2011 |
METHOD OF PRODUCING PHOTOELECTRIC CONVERSION ELEMENT, PHOTOELECTRIC
CONVERSION ELEMENT, AND PHOTOELECTROCHEMICAL CELL
Abstract
A method of producing a photoelectric conversion element, which
the element contains an electrically conductive support, a
photosensitive layer having porous semiconductor fine particles, a
charge transfer layer; and a counter electrode, includes the steps
of: applying a semiconductor dispersion liquid, in which the
content of solids excluding semiconductor fine particles is 10% by
mass or less based on the total amount of the dispersion liquid, on
the support, to form a coating; heating the coating, to obtain
porous semiconductor fine particles; and sensitizing the porous
particles by adsorption of the following dye: ##STR00001## wherein
A represents a group of atoms necessary for forming a ring; at
least one of Y.sup.1 and Y.sup.2 represents an acidic group and the
other represents an electron-attracting group; D represents a dye
residue; n represents 1 or a greater integer; L represents a single
bond or divalent linking group; and Y.sup.3 represents an acidic
group.
Inventors: |
KOBAYASHI; Katsumi;
(Odawara-shi, JP) ; TANI; Yukio; (Odawara-shi,
JP) ; KIMURA; Keizo; (Odawara-shi, JP) |
Assignee: |
FUJIFILM Corporation
Tokyo
JP
|
Family ID: |
43234271 |
Appl. No.: |
12/888820 |
Filed: |
September 23, 2010 |
Current U.S.
Class: |
429/111 ;
136/263 |
Current CPC
Class: |
H01L 51/0061 20130101;
H01L 51/0068 20130101; H01L 51/0059 20130101; Y02E 10/542 20130101;
C09B 23/0091 20130101; H01G 9/2013 20130101; C09B 23/04 20130101;
Y02E 10/549 20130101; H01L 51/0064 20130101; H01L 51/0062
20130101 |
Class at
Publication: |
429/111 ;
136/263 |
International
Class: |
H01M 14/00 20060101
H01M014/00; H01L 51/46 20060101 H01L051/46; H01M 6/30 20060101
H01M006/30 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2009 |
JP |
2009-223451 |
Claims
1. A method of producing a photoelectric conversion element, which
the photoelectric conversion element comprises a laminated
structure including: an electrically conductive support; a
photosensitive layer having porous semiconductor fine particles
that have adsorbed a dye, formed on the electrically conductive
support; a charge transfer layer; and a counter electrode;
comprising the steps of: applying a semiconductor fine particle
dispersion liquid, in which the content of solids excluding
semiconductor fine particles is 10% by mass or less based on the
total amount of the semiconductor fine particle dispersion liquid,
on the electrically conductive support, to form a coating; heating
the coating, to obtain porous semiconductor fine particles; and
sensitizing the porous semiconductor fine particles by adsorption
of a dye represented by formula (1): ##STR00024## wherein A
represents a group of atoms necessary for forming a ring together
with the carbon-nitrogen bond; at least one of Y.sup.1 and Y.sup.2
represents an acidic group, and when both of them represent an
acidic group, they may be identical with or different from each
other; one of Y.sup.1 and Y.sup.2 is an acidic group, the other one
represents an electron-attracting group; D represents a dye
residue; n represents an integer of 1 or greater; L represents a
single bond or a divalent linking group; and Y.sup.3 represents an
acidic group.
2. The method of producing a photoelectric conversion element
according to claim 1, wherein the electrically conductive support
is formed of an electrically conductive polymeric material.
3. The method of producing a photoelectric conversion element
according to claim 1, wherein the electrically conductive support
applied with the semiconductor fine particle dispersion liquid is
heated at a temperature ranging from 100.degree. C. to 250.degree.
C.
4. The method of producing a photoelectric conversion element
according to claim 1, wherein the dye represented by formula (1) is
a dye having a structure represented by any one of formulae (2) to
(5): ##STR00025## wherein at least one of Y.sup.1 and Y.sup.2
represents an acidic group, and when both of them represent an
acidic group, they may be identical with or different from each
other; one of Y.sup.1 and Y.sup.2 is an acidic group, the other one
represents an electron-attracting group; LL represents a divalent
linking group comprising at least one selected from the group
consisting of an alkenylene group, an alkynylene group and an
arylene group; Y.sup.3 represents an acidic group; R, R.sup.1,
R.sup.2 and R.sup.3 each independently represent a hydrogen atom,
an aliphatic group, an aromatic group, or a heterocyclic group
linked through a carbon atom; and R.sup.1 and R.sup.2 may form a
ring together with the substituent present on LL.
5. The method of producing a photoelectric conversion element
according to claim 4, wherein the dye represented by formula (2) is
a dye represented by formula (6): ##STR00026## wherein at least one
of Y.sup.1 and Y.sup.2 represents an acidic group, and when both of
them represent an acidic group, they may be identical with or
different from each other; one of Y.sup.1 and Y.sup.2 is an acidic
group, the other one represents an electron-attracting group; LL'
represents a single bond, or a divalent linking group comprising at
least one selected from the group consisting of an alkenylene
group, an alkynylene group and an arylene group; Y.sup.3 represents
an acidic group; R.sup.3 and R.sup.4 each independently represent a
hydrogen atom, an aliphatic group, an aromatic group, or a
heterocyclic group linked through a carbon atom; and B represents a
group of atoms needed for forming a ring together with the two
carbon atoms and the nitrogen atom on the benzene ring.
6. The method of producing a photoelectric conversion element
according to claim 4, wherein the dye represented by formula (5) is
a dye represented by formula (7): ##STR00027## wherein at least one
of Y.sup.1 and Y.sup.2 represents an acidic group, and when both of
them represent an acidic group, they may be identical with or
different from each other; one of Y.sup.1 and Y.sup.2 is an acidic
group, the other one represents an electron-attracting group; LL'
represents a single bond, or a divalent linking group comprising at
least one selected from the group consisting of an alkenylene
group, an alkynylene group and an arylene group; Y.sup.3 represents
an acidic group; R, R.sup.3 and R.sup.4 each independently
represent a hydrogen atom, an aliphatic group, an aromatic group,
or a heterocyclic group linked through a carbon atom; and B
represents a group of atoms needed for forming a ring together with
the two carbon atoms and the nitrogen atom on the benzene ring.
7. The method for producing a photoelectric conversion material
according to claim 1, wherein the acidic group for Y.sup.1 and
Y.sup.2 is a carboxyl group.
8. The method of producing a photoelectric conversion element
according to claim 1, wherein the content of solids excluding
semiconductor fine particles is 0.5% by mass or less based on the
total amount of the semiconductor fine particle dispersion
liquid
9. The method of producing a photoelectric conversion element
according to claim 2, wherein the electrically conductive polymeric
material is at least one kind of member selected from the group
consisting of polyethylene naphthalate, polyphenylene sulfide,
polycarbonate and polyether imide.
10. The method of producing a photoelectric conversion element
according to claim 3, wherein the temperature for heating the
electrically conductive support is from 120.degree. C. to
150.degree. C.
11. The method of producing a photoelectric conversion element
according to claim 1, wherein L in formula (1) is a methylene
group.
12. The method of producing a photoelectric conversion element
according to claim 1, wherein, in formula (1), one of Y.sup.1 and
Y.sup.2 is an acidic group and the other is an electron-attracting
group.
13. A photoelectric conversion element, which is produced by the
method according to claim 1.
14. A photoelectrochemical cell, comprising the photoelectric
conversion element according to claim 13.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method of producing a
photoelectric conversion element having high conversion efficiency,
a photoelectric conversion element, and a photoelectrochemical
cell.
BACKGROUND OF THE INVENTION
[0002] Photoelectric conversion elements are used in various
photosensors, copying machines, solar cells, and the like. These
photoelectric conversion elements have adopted various systems to
be put into use, such as elements utilizing metals, elements
utilizing semiconductors, elements utilizing organic pigments or
dyes, or combinations of these elements. Among them, solar cells
that make use of non-exhaustive solar energy do not necessitate
fuels, and full-fledged practicalization of solar cells as an
inexhaustible clean energy is being highly expected. Under such
circumstances, research and development of silicon-based solar
cells have long been in progress. Many countries also support
policy-wise considerations, and thus dissemination of silicon-based
solar cells is still in progress. However, silicon is an inorganic
material, and has limitations per se in terms of throughput and
molecular modification.
[0003] As a next-generation technology to solve such problems as
described above, research is being vigorously carried out on
dye-sensitized solar cells. Particularly, Graetzel et al. at
l'Ecole Polytechnique de l'Universite de Lausanne in Switzerland
have developed a dye-sensitized solar cell in which a dye formed
from a ruthenium complex is fixed at the surface of a porous
titanium oxide thin film, and have realized a conversion efficiency
that is comparable to that of amorphous silicon. Thus, they
instantly attracted the attention of researchers all over the
world.
[0004] U.S. Pat. No. 5,463,057, U.S. Pat. No. 5,525,440 and
JP-A-7-249790 ("JP-A" means unexamined published Japanese patent
application) describe dye-sensitized photoelectric conversion
elements making use of semiconductor fine particles sensitized by a
dye, to which the foregoing technology has been applied. These
dye-sensitized photoelectric conversion elements are produced by
applying a high-viscosity dispersion liquid containing
semiconductor fine particles on an electrode support, volatilizing
the solvent from the applied dispersion liquid at a relatively high
temperature (e.g., 400.degree. C. to 500.degree. C.), and adsorbing
a dye thereto. However, the time or energy consumed in this solvent
volatilization process poses an obstruction to cost reduction.
Furthermore, since the type of the electrode support that supports
the semiconductor fine particle layer is limited, it is difficult
to form an electrode layer on a plastic substrate or the like.
[0005] In regard to this problem, JP-A-2002-280587 describes a
method of adsorbing a ruthenium complex dye to semiconductor fine
particles, by applying on a support a dispersion liquid in which
the content of additives excluding semiconductor fine particles and
dispersion solvent is 1% by mass or less of the dispersion liquid,
and heating the dispersion liquid coating at 250.degree. C. or
below. However, the ruthenium complex dyes used in the sensitized
dyes are very expensive. Furthermore, there are concerns about the
supply of ruthenium, and it still cannot be said that this
technology is satisfactory as a next-generation technology
supporting clean energy to cope with the above-described problems
in a full-fledged manner. Rather, the research and development
intended for practicalization has been just begun to some
extent.
[0006] For such reasons, development of a photoelectric conversion
element which is sensitized by an organic material that is
inexpensive and is less restricted in resources, and which has
sufficient conversion efficiency, is desired. Reports are beginning
to emerge on the use of organic dyes as sensitizers of a
photoelectric conversion element (see JP-A-2008-135197). However,
this is a method for forming a porous semiconductor fine particle
layer at a high temperature of 500.degree. C.
SUMMARY OF THE INVENTION
[0007] The present invention resides in a method of producing a
photoelectric conversion element,
which the photoelectric conversion element comprises a laminated
structure including:
[0008] an electrically conductive support;
[0009] a photosensitive layer having porous semiconductor fine
particles that have adsorbed a dye, formed on the electrically
conductive support;
[0010] a charge transfer layer; and
[0011] a counter electrode;
comprising the steps of:
[0012] applying a semiconductor fine particle dispersion liquid, in
which the content of solids excluding semiconductor fine particles
is 10% by mass or less based on the total amount of the
semiconductor fine particle dispersion liquid, on the electrically
conductive support, to form a coating;
[0013] heating the coating, to obtain porous semiconductor fine
particles; and
[0014] sensitizing the porous semiconductor fine particles by
adsorption of a dye represented by formula (1):
##STR00002##
[0015] wherein A represents a group of atoms necessary for forming
a ring together with the carbon-nitrogen bond; at least one of
Y.sup.1 and Y.sup.2 represents an acidic group, and when both of
them represent an acidic group, they may be identical with or
different from each other; one of Y.sup.1 and Y.sup.2 is an acidic
group, the other one represents an electron-attracting group; D
represents a dye residue; n represents an integer of 1 or greater;
L represents a single bond or a divalent linking group; and Y.sup.3
represents an acidic group.
[0016] Further, the present invention resides in a photoelectric
conversion element, which is produced by the method described
above.
[0017] Further, the present invention resides in a
photoelectrochemical cell, comprising the photoelectric conversion
element described.
[0018] Other and further features and advantages of the invention
will appear more fully from the following description,
appropriately referring to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a cross-sectional view schematically showing an
exemplary embodiment of the photoelectric conversion element
produced by the method according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The inventors of the present invention conducted thorough
investigations, and as a result, they found that when a particular
dispersion liquid of semiconductor fine particles is applied and
dried on an electrically conductive support, and then the
semiconductor fine particles are sensitized with a particular dye,
a photoelectrochemical cell having high conversion efficiency can
be provided. The present invention was made based on this
finding.
[0021] According to the present invention, there is provided the
following means: [0022] <1> A method of producing a
photoelectric conversion element, which the photoelectric
conversion element comprises a laminated structure including:
[0023] an electrically conductive support,
[0024] a photosensitive layer having porous semiconductor fine
particles that have adsorbed a dye, formed on the electrically
conductive support;
[0025] a charge transfer layer; and
[0026] a counter electrode;
comprising the steps of:
[0027] applying a semiconductor fine particle dispersion liquid, in
which the content of solids excluding semiconductor fine particles
is 10% by mass or less based on the total amount of the
semiconductor fine particle dispersion liquid, on the electrically
conductive support, to form a coating;
[0028] heating the coating, to obtain porous semiconductor fine
particles; and
[0029] sensitizing the porous semiconductor fine particles by
adsorption of a dye represented by formula (1):
##STR00003##
[0030] wherein A represents a group of atoms necessary for forming
a ring together with the carbon-nitrogen bond; at least one of
Y.sup.1 and Y.sup.2 represents an acidic group, and when both of
them represent an acidic group, they may be identical with or
different from each other; one of Y.sup.1 and Y.sup.2 is an acidic
group, the other one represents an electron-attracting group; D
represents a dye residue; n represents an integer of 1 or greater;
L represents a single bond or a divalent linking group; and Y.sup.3
represents an acidic group. [0031] <2> The method of
producing a photoelectric conversion element described in the above
item <1>, wherein the electrically conductive support is
formed of an electrically conductive polymeric material. [0032]
<3> The method of producing a photoelectric conversion
element described in the above item <1> or <2>, wherein
the electrically conductive support applied with the semiconductor
fine particle dispersion liquid is heated at a temperature ranging
from 100.degree. C. to 250.degree. C. [0033] <4> The method
of producing a photoelectric conversion element described in any
one of the above items <1> to <3>, wherein the dye
represented by formula (1) is a dye represented by any one of
formulae (2) to (5):
##STR00004##
##STR00005##
[0034] wherein at least one of Y.sup.1 and Y.sup.2 represents an
acidic group, and when both of them represent an acidic group, they
may be identical with or different from each other; one of Y.sup.1
and Y.sup.2 is an acidic group, the other one represents an
electron-attracting group; LL represents a divalent linking group
comprising at least one selected from the group consisting of an
alkenylene group, an alkynylene group and an arylene group; Y.sup.3
represents an acidic group; R, R.sup.1, R.sup.2 and R.sup.3 each
independently represent a hydrogen atom, an aliphatic group, an
aromatic group, or a heterocyclic group linked through a carbon
atom; and R.sup.1 and R.sup.2 each may form a ring together with a
substituent(s) present on LL. [0035] <5> The method of
producing a photoelectric conversion element described in the above
item <4>, wherein the dye represented by formula (2) is a dye
represented by formula (6):
##STR00006##
[0036] wherein at least one of Y.sup.1 and Y.sup.2 represents an
acidic group, and when both of them represent an acidic group, they
may be identical with or different from each other; one of Y.sup.1
and Y.sup.2 is an acidic group, the other one represents an
electron-attracting group; LL' represents a single bond, or a
divalent linking group comprising at least one selected from the
group consisting of an alkenylene group, an alkynylene group and an
arylene group; Y.sup.3 represents an acidic group; R.sup.3 and
R.sup.4 each independently represent a hydrogen atom, an aliphatic
group, an aromatic group, or a heterocyclic group linked through a
carbon atom; and B represents a group of atoms needed for forming a
ring together with the two carbon atoms and the nitrogen atom on
the benzene ring. [0037] <6> The method of producing a
photoelectric conversion element described in the above item
<4>, wherein the dye represented by formula (5) is a dye
represented by formula (7):
##STR00007##
[0038] wherein at least one of Y.sup.1 and Y.sup.2 represents an
acidic group, and when both of them represent an acidic group, they
may be identical with or different from each other; one of Y.sup.1
and Y.sup.2 is an acidic group, the other one represents an
electron-attracting group; LL' represents a single bond, or a
divalent linking group comprising at least one selected from the
group consisting of an alkenylene group, an alkynylene group and an
arylene group; Y.sup.3 represents an acidic group; R, R.sup.3 and
R.sup.4 each independently represent a hydrogen atom, an aliphatic
group, an aromatic group, or a heterocyclic group linked through a
carbon atom; and B represents a group of atoms needed for forming a
ring together with the two carbon atoms and the nitrogen atom on
the benzene ring. [0039] <7> The method for producing a
photoelectric conversion material according to any one of the items
<1> to <6>, wherein the acidic group for Y.sup.1 and
Y.sup.2 is a carboxyl group. [0040] <8> A photoelectric
conversion element, which is produced by the method described in
any one of the above items <1> to <7>. [0041] <9>
A photoelectrochemical cell, comprising the photoelectric
conversion element described in the above item <8>.
[0042] The inventors of the present invention have devotedly
conducted investigations, and as a result, they found that a
photoelectric conversion element having high conversion efficiency
can be produced by producing a photoelectric conversion element by
a method including the steps of applying a semiconductor fine
particle dispersion liquid in which the content of solids excluding
semiconductor fine particles is equal to or less than a particular
amount, on an electrically conductive support mentioned above;
heating the dispersion liquid coating to obtain porous
semiconductor fine particles; and sensitizing the porous
semiconductor fine particles with a particular dye.
[0043] A preferred exemplary embodiment of the photoelectric
conversion element produced by the method of the present invention
will be explained with reference to the drawing. As shown in FIG.
1, the photoelectric conversion element 10 includes an electrically
conductive support 1; a photosensitive layer 2 provided on the
electrically conductive support 1, the photosensitive layer having
porous semiconductor fine particles to which a dye has been
adsorbed; a charge transfer layer 3; and a counter electrode 4. The
electrically conductive support 1 having a photosensitive layer 2
provided thereon functions as a working electrode in the
photoelectric conversion element 10. This photoelectric conversion
element 10 can be operated as a photoelectrochemical cell (not
depicted) by making the element usable in a cell application where
the cell is made to work with an external circuit 6.
[0044] A light-receiving electrode 5 is an electrode comprising an
electrically conductive support 1; and a photosensitive layer
(semiconductor film) 2 coated on the electrically conductive
support, the layer containing semiconductor fine particles 22 to
which a dye 21 has been adsorbed. A light incident to the
photosensitive layer (semiconductor film) 2 excites the dye. The
excited dye has electrons with high energy, and these electrons are
transported from the dye 21 to the conduction band of the
semiconductor fine particles 22 and further reach the electrically
conductive support 1 by diffusion. At this time, the molecules of
the dye 21 are in an oxide form; however, in a photoelectrochemical
cell, the electrons on the electrode return to the oxide of the dye
while working in the external circuit, while the light-receiving
electrode 5 works as a negative electrode of this cell.
[0045] The materials used in the photoelectric conversion element
of the present invention and the method of producing the
photoelectric conversion element will be described below in
detail.
(A) Electrically Conductive Support
[0046] The method of producing a photoelectric conversion element
of the present invention makes use of an electrically conductive
support. As the electrically conductive support, a support having
electroconductivity per se, such as a metal, or a glass or
polymeric material having an electrically conductive layer on the
surface can be used. It is preferable that the electrically
conductive support is substantially transparent. The terms
"substantially transparent" means that the transmittance of light
is 10% or more, preferably 50% or more, particularly preferably 80%
or more. As the electrically conductive support, a support formed
from glass or a polymeric material and coated with an electrically
conductive metal oxide is preferable. In this case, the amount of
coating of the conductive metal oxide is preferably 0.1 to 100 g
per square meter of the support made of glass or a polymeric
material. In the case of using a transparent conductive support, it
is preferable that light is incident from the support side.
Examples of the polymeric material that may be preferably used
include tetraacetylcellulose (TAC), polyethylene terephthalate
(PET), polyethylene naphthalate (PEN), syndiotactic polystyrene
(SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate
(PAR), polysulfone (PSF), polyester sulfone (PES), polyether imide
(PEI), cyclic polyolefin, and phenoxy bromide. The electrically
conductive support may be provided with a light management function
at the surface, and for example, the anti-reflective film having a
high refractive index film and a low refractive index oxide film
alternately laminated as described in JP-A-2003-123859, and the
light guide function as described in JP-A-2002-260746 may be
mentioned.
[0047] It is preferable to provide the electrically conductive
support with a function of blocking ultraviolet light. For
instance, there may be mentioned a method of adopting a fluorescent
material that is capable of changing ultraviolet light to visible
light as described in JP-A-2001-185242, within the transparent
support or on the surface of the transparent support. As another
preferred method, a method of using an ultraviolet absorbent may
also be used. Preferred examples thereof include those described
in, for example, JP-A-11-345991, JP-A-2002-25634, JP-A-2003-21769,
JP-A-2004-227843, JP-A-2004-349129, JP-A-2002-134178 and
JP-A-2003-100358.
[0048] The conductive support may also be imparted with the
functions described in JP-A-11-250944, JP-A-2003-308892 and
JP-A-2003-282163.
[0049] Preferred examples of the electrically conductive film
include films of metals (for example, platinum, gold, silver,
copper, aluminum, rhodium, and indium), carbon, and electrically
conductive metal oxides (for example, indium-tin composite oxide,
and fluorine-doped tin oxide). Preferred examples of the
electrically conductive film and the producing method of the same
include those described in, for example, JP-A-2003-151355,
JP-A-2004-311174, JP-A-2004-311175, JP-A-2004-311176,
JP-A-2005-85699, JP-A-2005-85670, JP-A-2005-116391,
JP-A-2003-323818, JP-A-2004-165080, and JP-A-2005-141981.
[0050] The thickness of the conductive film layer is preferably
0.01 to 30 .mu.m, more preferably 0.03 to 25 .mu.m, and
particularly preferably 0.05 to 20 .mu.m.
[0051] In the present invention, an electrically conductive support
having lower surface resistance is preferred. The surface
resistance is preferably in the range of 50 .OMEGA./cm.sup.2 or
less, and more preferably 10 .OMEGA./cm.sup.2 or less. The lower
limit of the surface resistance is not particularly limited, but
the lower limit is usually about 0.1 .OMEGA./cm.sup.2.
[0052] Since the resistance value of the electrically conductive
film is increased as the cell area increases, a collecting
electrode may be disposed. Preferred examples of the shape and
material of the collecting electrode include those described in,
for example, JP-A-11-266028, JP-A-2005-108467, JP-A-2003-203681,
JP-A-2004-146425, JP-A-2004-128267, JP-A-2004-164970,
JP-A-2004-327226, JP-A-2004-164950, JP-A-2005-78857,
JP-A-2005-197176, JP-A-2004-164950, JP-A-2000-285977,
JP-A-2002-314108, and JP-A-2003-123858.
[0053] As described in JP-A-2000-285974, a gas barrier film and/or
an ion diffusion preventing film may be disposed between the
support and the transparent conductive film. The gas barrier layer
may be any of a resin film (see, for example, JPA-2000-282163 or
JP-A-2005-142086) or an inorganic film (see, for example,
JPA-2005-142086).
[0054] Furthermore, a transparent electrode and a porous
semiconductor electrode photocatalyst-containing layer may also be
provided, as described in JP-A-2005-142084 or JP-A-2005-142085.
[0055] The transparent conductive layer may have a laminate
structure, and preferred examples of the production method include
the method of laminating FTO on ITO as described in
JP-A-2003-323818, as well as the methods described in
JP-A-2005-44544, JP-A-2005-142088, JP-A-2005-19205,
JP-A-2004-241228 and JP-A-2004-319872.
(B) Semiconductor Fine Particles
[0056] In the method of producing a photoelectric conversion
element of the present invention, a semiconductor fine particle
dispersion liquid in which the content of solids excluding
semiconductor fine particles is 10% by mass or less of the whole
semiconductor fine particle dispersion liquid, is applied on the
electrically conductive support as described above and heated, and
thus porous semiconductor fine particles are obtained.
[0057] Regarding the semiconductor fine particles, fine particles
of chalcogenides of metals (for example, oxides, sulfides and
selenides), or fine particles of perovskites may be used with
preference. Preferred examples of the chalcogenides of metals
include oxides of titanium, tin, zinc, tungsten, zirconium,
hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium,
niobium or tantalum, cadmium sulfide, and cadmium selenide.
Preferred examples of the perovskites include strontium titanate,
and calcium titanate. Among these, titanium oxide, zinc oxide, tin
oxide, and tungsten oxide are particularly preferred.
[0058] Semiconductors are classified into n-type semiconductors in
which the carrier associated with conduction is electron, or p-type
semiconductors in which the carrier is hole. It is preferable to
use an n-type semiconductor in the present invention, in view of
the conversion efficiency. The n-type semiconductors include an
intrinsic semiconductor (or true semiconductor) which does not have
an impurity level, and has equal concentrations of the carriers
consisting of the conduction band electrons and the valence band
holes, as well as an n-type semiconductor having a higher
concentration of the electron carrier due to the structural defect
originating from impurities. Examples of the n-type inorganic
semiconductors that may be preferably used in the present invention
include TiO.sub.2, TiSrO.sub.3, ZnO, Nb.sub.2O.sub.3, SnO.sub.2,
WO.sub.3, Si, CdS, CdSe, V.sub.2O.sub.5, ZnS, ZnSe, SnSe,
KTaO.sub.3, FeS.sub.2, PbS, InP, GaAs, CuInS.sub.2, and
CuInSe.sub.2. Among these, most preferred examples of the n-type
semiconductors include TiO.sub.2, ZnO, SnO.sub.2, WO.sub.3 and
Nb.sub.2O.sub.3. A composite semiconductor material composed of
plural kinds of these semiconductors is also used with
preference.
[0059] The particle size of the semiconductor fine particles is
such that, for the purpose of maintaining the viscosity of the
semiconductor fine particle dispersion liquid high, the average
particle size of the primary particles is preferably from 2 nm to
50 nm, and it is more preferable that the semiconductor fine
particles are ultrafine particles having an average particle size
of the primary particles of from 2 nm to 30 nm. Two or more kinds
of fine particles having different particle size distributions may
be used in mixture, and in this case, it is preferable that the
average size of the smaller particles is 5 nm or less. Also, for
the purpose of enhancing the light-capturing rate by scattering the
incident light, large particles having an average particle size of
more than 50 nm can be added at a low proportion based on the
ultrafine particles described above. In this case, the content of
the large particles is preferably 50% or less, and more preferably
20% or less, by mass of the content of the particles having an
average particle size of 50 nm or less. The average particle size
of the large particles that are added and mixed for the purpose
described above is preferably 100 nm or more, and more preferably
250 nm or more.
[0060] In regard to the method for producing semiconductor fine
particles, sol-gel methods described in, for example, Sakka, Sumio,
"Science of Sol-Gel Processes", Agne Shofu Publishing, Inc. (1998)
and Technical Information Institute Co., Ltd., "Thin Film Coating
Technology Based on Sol-Gel Processes" (1995); and a gel-sol method
described in, for example, Sugimoto, Tadao, "Synthesis of
Monodisperse Particles and Control of Size and Shape by Gel-Sol
Process, a New Synthesis Method", Materia Japan, Vol. 35, No. 9,
pp. 1012-1018 (1996), are preferred. It is also preferable to use a
method developed by Degussa GmbH, in which a chloride is hydrolyzed
at high temperature in an acid hydride salt to produce an oxide.
When the semiconductor fine particles are titanium oxide, the
sol-gel method, the gel-sol method, and the method of hydrolyzing a
chloride in an acid hydride salt at high temperature, are all
preferred, and the sulfuric acid method and chlorine method
described in Seino, Manabu, "Titanium Oxide: Material Properties
and Application Technologies", Gihodo Shuppan Co., Ltd. (1997) may
also be used. Other preferred examples of the sol-gel method
include the method described in Barbe et al., Journal of American
Ceramic Society, Vol. 80, No. 12, pp. 3157-3171 (1997), and the
method described in Burnside et al., Chemistry of Materials, Vol.
10, No. 9, pp. 2419-2425.
[0061] In addition to these, examples of the method of producing
the semiconductor fine particles include, as preferred methods for
producing titania nanoparticles, a method based on flame hydrolysis
of titanium tetrachloride (see, for example, JP-T-6-511113 ("JP-T"
means searched and published International patent publication)), a
method of combusting titanium tetrachloride (see, for example,
JP-A-2003-327432), a method of hydrolyzing a stable chalcogenide
complex (see, for example, JP-A-2001-85076), hydrolysis of
orthotitanic acid (see, for example, JP-A-2004-161589 and
JP-A-2004-238213), a method of forming semiconductor fine particles
from a soluble portion and an insoluble portion, and then removing
by dissolving the soluble portion (see, for example,
JP-A-2002-246620), hydrothermal synthesis of an aqueous peroxide
solution (see, for example, JP-A-2003-92154), and a method of
producing titanium oxide fine particles having a core-shell
structure according to a sol-gel method (see, for example,
JP-A-2004-10403).
[0062] Examples of the crystal structure of titania include
structures of anatase type, brookite type and rutile type, and
anatase type and brookite type structures are preferred in the
present invention. Preferred examples include the structure
examples described in JP-A-11-339867, JP-A-2001-43907, and
JP-A-2001-43907, and the titania having the above-identified
structure described in JP-A-11-339867, JP-A-2001-43907, and
JP-A-2001-43907 may be incorporated herein by reference. Preferred
examples of the properties of titanium oxide include the examples
described in EP 1 338 563, US 2004/0161380, U.S. Pat. No.
6,075,203, U.S. Pat. No. 6,444,189, U.S. Pat. No. 6,720,202,
Chinese Patent 1540772(A), JP-A-2001-283942, and
JP-A-2001-212457.
[0063] It is also acceptable to mix a titania
nanotube/nanowire/nanorod with the titania fine particles.
Preferred examples thereof include those described in, for example,
JP-A-2003-168495, JP-A-2003-251194, JP-A-2004-175586,
JP-A-2004-175587, JP-A-2004-175588, JP-A-2004-311354,
JP-A-2004-311355, JP-A-2004-319661, and JP-A-2005-162584.
[0064] Titania may be doped with a non-metallic element or the
like. Preferred examples thereof include those described in, for
example, JP-A-2000-235874, JP-A-2003-252624, JP-A-2002-25637,
JP-A-2003-187881, JP-A-2003-187882, JP-A-2003-179244,
JP-A-2004-87148, JP-A-2004-119279, JP-A-2005-93944,
JP-A-2005-64493, JP-A-2003-257507, and JP-A-2003-323920. In
addition to the dopants, as additives used with titania, a binder
for improving necking, or a surface additive for preventing reverse
electron transfer may also be used. Preferred examples of the
additives include ITO or SnO particles (see, for example,
JP-A-11-283682 and JP-A-2001-345125), whiskers (see, for example,
JP-A-2003-163037), a fibrous graphite/carbon nanotube (see, for
example, JP-A-2003-163037), a zinc oxide necking coupler (see, for
example, JP-A-2003-273381), fibrous materials such as celluloses
(see, for example, JP-A-2003-123861), metals (see, for example,
JP-A-2000-285975 and JP-A-2001-35551), organosilicon (see, for
example, JP-A-2000-294304), dodecyl benzenesulfonate (see, for
example, JP-A-2000-260493), charge transfer coupling molecules of
silane compounds or the like (see, for example, JP-A-2000-323192
and JP-A-2001-102103), and a potential gradient type dendrimer
(see, for example, JP-A-2004-213908).
[0065] For the purpose of eliminating surface defects of titania,
or the like, titania may be subjected to an acid base treatment or
an oxidation reduction treatment before the adsorption of a dye.
Preferred examples of the acid base treatment include those
described in, for example, JP-A-2000-101106, JP-A-2002-293541,
JP-A-2003-297441, JP-A-2003-297442, and JP-A-2004-235240.
Furthermore, titania may also be subjected to etching, an oxidation
treatment, a hydrogen peroxide treatment, a dehydrogenation
treatment, UV-ozone, oxygen plasma or the like, as described in
JP-A-8-81222, JP-A-2000-285980, JP-A-2004-158243, JP-A-2004-247104,
and the like.
(C) Semiconductor Fine Particle Dispersion Liquid
[0066] The method of producing a photoelectric conversion element
of the present invention includes a step of obtaining porous
semiconductor fine particles by applying a semiconductor fine
particle dispersion liquid in which the content of solids excluding
semiconductor fine particles is 10% by mass or less of the total
amount of the semiconductor fine particle dispersion liquid, on the
electrically conductive support mentioned above, and appropriately
heating the coated support.
[0067] Examples of the method of producing a semiconductor fine
particle dispersion liquid include, in addition to the sol-gel
method described above, a method of precipitating the semiconductor
in the form of fine particles in a solvent upon synthesis and
directly using the fine particles; a method of ultrasonicating fine
particles, and thereby pulverizing the fine particles into
ultrafine particles; a method of mechanically grinding a
semiconductor using a mill or a mortar, and pulverizing the ground
semiconductor; and the like. As a dispersion solvent, water and/or
various organic solvents can be used. Examples of the organic
solvent include alcohols such as methanol, ethanol, isopropyl
alcohol, citronellol and terpineol; ketones such as acetone; esters
such as ethyl acetate; dichloromethane, and acetonitrile.
[0068] At the time of dispersing the fine particles, for example, a
polymer such as polyethylene glycol, hydroxyethylcellulose or
carboxymethylcellulose; a surfactant, an acid or a chelating agent
may be used in a small amount as a dispersing aid, as necessary. It
is preferable that such a dispersing aid is mostly eliminated
before the step of forming a film on the electrically conductive
support, by a filtration method, a method of using a separating
membrane, or a centrifugation method. The semiconductor fine
particle dispersion liquid used in the present invention is such
that the content of solids excluding semiconductor fine particles
is 10% by mass or less based on the total amount of the dispersion
liquid. This concentration is preferably 5% or less, more
preferably 3% or less, further preferably 1% or less, furthermore
preferably 0.5% or less, and particularly preferably 0.3% or less.
In other words, the semiconductor fine particle dispersion liquid
may contain a solvent and solids excluding semiconductor fine
particles in an amount of 10% by mass or less based on the total
amount of the semiconductor fine particle dispersion liquid. In the
present, it is preferable that the semiconductor fine particle
dispersion liquid is substantially composed of semiconductor fine
particles and a dispersion solvent. If the content of solids
excluding semiconductor fine particles in the semiconductor fine
particle dispersion liquid is too high, the conversion efficiency
is decreased, and it is not preferable.
[0069] If the viscosity of the semiconductor fine particle
dispersion liquid is too high, the dispersion liquid undergoes
aggregation, and film formation cannot be achieved. On the other
hand, if the viscosity of the semiconductor fine particle
dispersion liquid is too low, the liquid flows out, and film
formation cannot be achieved. Therefore, the viscosity of the
dispersion liquid is preferably 10 to 300 Ns/m.sup.2 at 25.degree.
C., and more preferably 50 to 200 Ns/m.sup.2 at 25.degree. C.
[0070] In regard to the method of applying the semiconductor fine
particle dispersion liquid, a roller method, a dipping method or
the like can be used as a method involving application.
Furthermore, an air knife method, a blade method or the like can be
used as a method involving metering. As a method that can equally
utilize a method involving application and a method involving
metering, a wire bar method disclosed in JP-B-58-4589 ("JP-B" means
examined Japanese patent publication), an extrusion method, a
curtain method and a slide hopper method described in U.S. Pat. No.
2,681,294, U.S. Pat. No. 2,761,419 and U.S. Pat. No. 2,761,791, and
the like are preferred. It is also preferable to apply the
dispersion liquid by a spinning method or a spray method, using a
versatile machine. Preferred examples of a wet printing method
include the three major printing methods of relief printing, offset
printing and gravure printing, as well as intaglio printing, rubber
plate printing, screen printing and the like. Among these, a
preferable film forming method is selected in accordance with the
liquid viscosity or the wet thickness. Furthermore, since the
semiconductor fine particle dispersion liquid used in the present
invention has high viscosity and has viscidity, the fine particle
dispersion liquid often has a strong cohesive power, and may not
have good affinity to the support upon coating. Under such
circumstances, when surface cleaning and hydrophilization are
carried out through a UV-ozone treatment, the affinity between the
applied semiconductor fine particle dispersion liquid and the
surface of the electrically conductive support increases, and thus
it becomes easier to apply the semiconductor fine particle
dispersion liquid.
[0071] The thickness of the entire semiconductor fine particle
layer is preferably 0.1 to 100 .mu.m, more preferably 1 to 30
.mu.m, and even more preferably 2 to 25 .mu.m. The amount of the
coated semiconductor fine particles per square meter of the support
is preferably 0.5 to 400 g, and more preferably 5 to 100 g.
[0072] The applied layer of semiconductor fine particles is
subjected to a heating treatment, for the purpose of reinforcing
the electronic contact between semiconductor fine particles and
enhancing the adhesiveness of the semiconductor fine particles to
the support, and also in order to dry the applied semiconductor
fine particle dispersion liquid. The porous semiconductor fine
particle layer can be formed by this heating treatment, and thus
conventional calcination processes are not needed. The temperature
range for the heating treatment is not particularly limited, but in
the case of using the electrically conductive polymer materials
mentioned above as the electrically conductive support (for
example, tetraacetyl cellulose (TAC), polyethylene terephthalate
(PET), polyethylene naphthalate (PEN), syndiotactic polystyrene
(SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate
(PAR), polysulfone (PSF), polyester sulfone (PES), polyetherimide
(PEI), cyclic polyolefin, and brominated phenoxy), the temperature
is preferably from 100.degree. C. to 250.degree. C.
[0073] For the purpose of reducing an increase in the resistance or
deformation due to the heating of the electrically conductive
support, a preferred temperature range is from 100.degree. C. to
150.degree. C., and more preferably from 120.degree. C. to
150.degree. C. When a support having a low melting point or a low
softening point is used as the electrically, conductive support, it
is preferable, as far as possible, to set the heat treatment
temperature at 150.degree. C. or less.
[0074] Furthermore, light energy can also be used in addition to
the heating treatment. For example, when titanium oxide is used for
the semiconductor fine particles, the surface may be activated by
providing the light that is absorbed by the semiconductor fine
particles, such as ultraviolet light, or only the surface of the
semiconductor fine particles can be activated with a laser light or
the like. When the semiconductor fine particles are irradiated with
a light that is absorbed by the fine particles, the impurities
adsorbed to the particle surfaces are decomposed as a result of
activation of the particle surfaces, and a state preferable for the
purpose described above can be attained. In the case of using the
heating treatment and ultraviolet light in combination, the heating
is carried out at a temperature of preferably from 100.degree. C.
to 250.degree. C., more preferably from 100.degree. C. to
150.degree. C., and further preferably from 120.degree. C. to
150.degree. C., while the semiconductor fine particles are
irradiated with the light that is absorbed by the fine particles.
As such, by inducing photoexcitation of the semiconductor fine
particles, the impurities incorporated in the fine particle layer
can be washed away by photodecomposition, and the physical bonding
between the fine particles can be reinforced.
[0075] In addition to the processes of applying the semiconductor
fine particle dispersion liquid on the electrically conductive
support and subjecting the semiconductor fine particles to heating
or light irradiation, other treatments may also be carried out.
Preferred examples of such treatments include the passage of
electric current, chemical treatment, and the like.
[0076] It is also acceptable to apply pressure after coating, and
examples of the method of applying pressure include the methods
described in JP-T-2003-500857, JP-A-2002-93475, JP-A-2003-282160
and JP-A-2004-214129. Examples of the light irradiation method
include the methods described in JP-A-2001-357896, JP-A-11-219734,
JP-A-2004-314313, JP-A-2005-142446, and JP-A-2001-247314. Examples
of the methods utilizing plasma, microwaves or electric current
include the methods described in JP-A-2002-353453,
JP-A-2003-308893, JP-A-2004-265662, JP-A-2004-327369,
JP-A-2004-342319, JP-A-2005-116415, JP-A-2005-139498, and
JPA-2004-273770. Examples of the chemical treatment include the
methods described in JP-A-2001-357896, JP-A-2002-280327,
JP-A-2003-281947, JP-T-2005-520314 and JP-A-2003-297442.
[0077] The method of coating the semiconductor fine particles on
the electrically conductive support is included in the (1) wet
methods, such as a method of applying a semiconductor fine particle
dispersion liquid on an electrically conductive support; and a
method of applying a precursor of the semiconductor fine particles
on an electrically conductive support, hydrolyzing the precursor
under the action of the moisture in air, and thereby obtaining a
semiconductor fine particle film, as described in Japanese Patent
No. 2664194. In regard to the production methods under the class of
wet method, examples of the method of preparing a dispersion liquid
of semiconductor fine particles include, in addition to the methods
described above, a method of pulverizing fine particles in a
mortar; a method of dispersing fine particles while pulverizing the
particles using a mill; a method of precipitating fine particles in
a solvent upon synthesizing a semiconductor, and directly using the
precipitates; and the like. Preferred examples thereof include
those described in, for example, JP-A-11-144772, JP-A-2005-100792,
EP 1 300 897 A1, JP-A-2002-324591, JP-A-2002-145615,
JP-A-2003-176130, and JP-A-2004-79610. The dispersion medium for
the coating liquid used in the (1) wet methods may be water, or
various organic solvents (for example, methanol, ethanol,
t-butanol, dichloromethane, acetone, acetonitrile and ethyl
acetate). Preferred examples thereof include those described in,
for example, JP-T-6-511113 ("JP-T" means published searched patent
publication), CN Patent No. 144292, JP-A-11-11912,
JP-A-2000-294814, JP-A-2000-319018, JP-A-2000-319018,
JP-A-2000-319018, JP-A-2002-145614, JP-A-2002-75477,
JP-A-2004-193321, WO 02/067357, JP-A-2004-207205, JP-A-2004-111348,
JP-A-2004-186144, JP-A-2003-282162, JP-A-2005-142011,
JP-A-2005-174695, JP-A-2005-85500, JP-A-11-343118, JP-A-11-354169,
JP-A-2000-106222, JP-A-2003-246621, JP-A-2003-51345,
JP-A-2004-158551, JP-A-2001-358348, and JP-A-2003-217693. Upon
dispersing the semiconductor fine particles, a polymer, a
surfactant, an acid, a chelating agent or the like may be used as a
dispersing aid as necessary, if used in a small amount.
[0078] As the method of coating semiconductor fine particles on an
electrically conductive support, (2) dry methods and (3) other
methods may be used together with the (1) wet methods described
above.
[0079] Preferred examples of the (2) dry methods include the
methods described in JP-A-2000-231943, JP-A-2002-170602,
JP-A-2001-345124, JP-A-2003-197280, JP-A-2003-123854,
JP-A-2003-123852, JP-A-2003-123853, JP-A-2005-39013,
JP-A-2004-39286, and JP-A-2005-104760.
[0080] Preferred examples of the (3) other methods include the
methods described in JP-A-2002-134435, US 2004/0123896,
JP-A-2004-327265, JP-A-2004-342397, JP-T-2003-500857,
JP-A-2005-85491, JP-A-2003-98977, JP-A-2002-299665,
JP-A-2003-243053, JP-A-2004-253331, JP-A-11-310898,
JP-A-2003-257507, JP-A-2003-323920, US 2004/0084080, US
2004/0121068, JP-A-2004-319873, JP-A-10-112337, JP-A-11-6098,
JP-A-2000-178791, JP-A-2000-178792, JP-A-2004-103420, and
JP-A-2003-301283.
[0081] It is preferable for the semiconductor fine particles to
have a large surface area, so that a large amount of dye can adsorb
to the surface. For example, while the semiconductor fine particles
have been coated on the support, the surface area is preferably 10
times or more, and more preferably 100 times or more, relative to
the projected surface area. The upper limit of this value is not
particularly limited, but the upper limit is usually about 5000
times. Preferred examples of the structure of the semiconductor
fine particles include the structures disclosed in JP-A-2001-93591,
JP-A-2001-257012, JP-A-2001-196106, JP-A-2001-273936, and EP No.
1207572 A1.
[0082] In general, as the thickness of the semiconductor fine
particle layer increases, the amount of dye that can be supported
per unit area increases, and therefore, the light absorption
efficiency is increased. However, since the diffusion distance of
generated electrons increases along, the loss due to charge
recombination is also increased. Although a preferred thickness of
the semiconductor fine particle layer may vary with the utility of
the element, the thickness is typically 0.1 to 100 .mu.m. In the
case of using the photoelectric conversion element as a
photoelectrochemical cell, the thickness of the semiconductor fine
particle layer is preferably 1 to 50 .mu.m, and more preferably 3
to 30 .mu.m. The semiconductor fine particles may be calcined after
being applied on the support, at a temperature of 100 to
800.degree. C. for 10 minutes to 10 hours, so as to bring about
cohesion of the particles.
[0083] When a glass support is used, the film forming temperature
is preferably 400 to 600.degree. C. When a plastic support is used,
it is preferable to form a film at 300.degree. C. or less, more
preferably 250.degree. C. or less. The method of forming a film at
250.degree. C. or less may be any of (1) a wet method, (2) a dry
method, and (3) an electrophoresis method (including an
electrocrystallization method); preferably (1) a wet method or (2)
a dry method; and more preferably (1) a wet method.
[0084] The wet method is a method of forming a film on a plastic
film by applying a semiconductor layer or a precursor thereof in a
wet manner or the like, and further activating the semiconductor
film. Examples of the wet method include the method of heating a
mixture of a semiconductor and an electrically conductive compound
at low temperature as described in JP-A-10-290018; a method of
utilizing a precursor (examples of the precursor include
(NH.sub.4).sub.2TiF.sub.6 described in JP-A-2001-110462; titanium
peroxide described in JP-A-2001-247314; and a metal alkoxide, a
metal complex and an organic acid metal salt described in
JP-A-11-219734); a method of applying a slurry additionally
containing a metal organic oxide (alkoxide or the like), and
forming a semiconductor film by a heating treatment, a light
treatment or the like, as described in JP-T-2005-520314; and a
method of characterizing the pH of the slurry additionally
containing an inorganic precursor described in JP-A-2003-2819847,
and the slurry described in JP-A-2005-56627, and the properties and
state of the dispersed titania particles.
[0085] These slurries may be added with a small amount of binder,
Examples of the binder include the celluloses described in
JP-A-2003-109678 or JP-A-2003-123861; the fluoropolymers described
in JP-A-2003-272722; the crosslinked rubber described in
JP-A-2004-47261; the polybutyl titanate described in
JP-T-2005-516365; and the carboxymethylcellulose described in
JP-A-2005-135798.
[0086] Examples of the technique related to the formation of a
layer of a semiconductor or a precursor thereof include a method of
hydrophilizing the layer by a physical method using corona
discharge, plasma, UV or the like; a chemical treatment based on an
alkali (see, for example, JP-A-2004-119120) or on polyethylene
dioxythiophene and polystyrenesulfonic acid (see, for example,
JP-A-2005-169228) or the like; formation of an intermediate film
for bonding of polyaniline or the like as described in
JP-A-2003-297443.
[0087] Examples of the dry method include deposition, sputtering,
an aerosol deposition method, and the like. Preferred examples
thereof include methods described in, for example, JP-A-2005-39013,
JP-A-2004-074609, Japanese Patent No. 3265481, JP-A-2003-100359,
and JP-A-2004-39286.
[0088] Furthermore, the electrophoresis method and the
electrocrystallization method described in JP-A-2002-100146 and
JP-A-2004-311354 may also be used.
[0089] Furthermore, a method of first preparing a DSC on a heat
resistant base, and then transferring the DSC to a film made of
plastic or the like, may be used. Preferably, a method of
transferring a semiconductor layer through EVA as described in
JP-A-2002-184475; a method of forming a semiconductor layer and a
conductive layer on a sacrificing base containing an inorganic salt
that can be removed by ultraviolet rays or a water-based solvent,
subsequently transferring the layers to an organic base, and
removing the sacrificing base as described in JP-A-2003-98977; and
the like may be used.
[0090] The amount of coating of the semiconductor fine particles
per square meter of the support is preferably 0.5 to 500 g, and
more preferably 5 to 100 g.
(D) Photosensitive Layer
[0091] In the method of producing a photoelectric conversion
element of the present invention, a photosensitive layer can be
obtained by adsorbing a particular dye to a porous semiconductor
fine particle layer which has been obtained by applying the
semiconductor fine particle dispersion liquid described above, on
the electrically conductive support described above, and heating
the semiconductor fine particle layer. The photosensitive layer is
designed according to the purpose, and may have a single layer
constitution or a multilayer constitution. Furthermore, the dye in
the photosensitive layer may be of one kind or may be a mixture of
plural kinds, but the (E) dye that will be described below is used
for at least one kind of the plural kinds. The photosensitive layer
of the photoelectric conversion element produced by the method of
the present invention contains semiconductor fine particles having
this dye adsorbed thereto, and has high sensitivity. When the
photoelectric conversion element is used as a photoelectrochemical
cell, a high conversion efficiency can be obtained.
(E) Dye
[0092] The method of producing a photoelectric conversion element
of the present invention includes a step of sensitizing the porous
semiconductor fine particles obtained by the process described
above, with a specific dye. A photoelectric conversion element
produced by a method including a step of sensitizing porous
semiconductor fine particles by adsorption of a dye (dye compound)
represented by formula (1), can exhibit high photoelectric
conversion efficiency.
##STR00008##
[0093] First, the dye represented by the formula (1), which is used
in the present invention, will be explained. This dye acts as a
sensitizing dye for the photoelectrochemical cell of the
invention.
[0094] Development of a dye used in dye-sensitized photoelectric
conversion elements has been traditionally focused mainly on the
donor site. There, attention was paid to a dye having a cyclic
compound introduced to the adsorption site, and thorough
investigations were made. As a result, it was found that there can
be provided a photoelectrochemical cell having high conversion
efficiency which is capable of absorbing up to a relatively long
wavelength region in the solar spectrum, by using a particular dye
(dye compound), as a sensitizing dye, in which a cyclic structure
formed from carbon atoms and nitrogen atoms has an acidic group
linked to the nitrogen atom of the cyclic structure via a single
bond or divalent linking group, and an exomethylene of the cyclic
structure is substituted with one or more acidic groups.
[0095] The dye represented by formula (1) for use in the present
invention will be explained. The dye acts as a sensitizing dye for
the photoelectrochemical cell of the present invention.
[0096] In formula (1), A represents a group of atoms necessary for
forming a ring together with the carbon-nitrogen bond. A preferred
example of the ring formed by A is a residue obtained by
eliminating a carbonyl group or a thiocarbonyl group from a
heterocyclic acidic nucleus. Examples of the heterocyclic acidic
nucleus include those described in, for example, T. H. James, "The
Theory of the Photographic Process, 4th edition", Macmillan
publishing, 1977, p. 199. More preferred examples of the ring
formed by A include residues obtained by eliminating a carbonyl
group or a thiocarbonyl group from rhodanine, hydantoin,
thiohydantoin, barbituric acid, thiobarbituric acid,
pyrazolidinedione, pyrazolone, indanedione or isoxazolone; even
more preferred examples include residues obtained by eliminating a
carbonyl group or a thiocarbonyl group from rhodanine, hydantoin,
thiohydantoin, barbituric acid or thiobarbituric acid; and a
particularly preferred example is residues obtained by eliminating
a carbonyl group or a thiocarbonyl group from rhodanine.
[0097] At least one of Y.sup.1 and Y.sup.2 represents an acidic
group, and when both of them represent an acidic group, they may be
identical with or different from each other. When only one of them
is an acidic group, the other one represents an electron-attracting
group. Y.sup.3 represents an acidic group.
[0098] In the present specification, the term "acidic group" means
a group in which the pKa value of the most acidic hydrogen atom
among the hydrogen atoms constituting the acidic group is 13 or
less. Examples of the acidic group include a carboxyl group, a
sulfo group, a phosphonic acid group, a phenolic hydroxyl group, an
alkylsulfonylcarbamoyl group, and a phosphoric acid group. The
acidic group is preferably a carboxyl group, a sulfo group, a
phosphonic acid group or a phenolic hydroxyl group; more preferably
a carboxyl group or a sulfo group; and particularly preferably a
carboxyl group.
[0099] The electron-withdrawing group may be a substituent having
the effects described below (-I effect and -M effect). In general,
an electron-withdrawing group attenuates the electron density at a
particular position of a molecule. The electron-withdrawing
property or electron-donating property cannot be explained only by
the difference in the electronegativity. That is, since an
excitation effect, a mesomeric effect and the like work together in
a compositive manner, the manifestation of the electron-withdrawing
property or the electron-donating property can vary with the
aromaticity, presence of a conjugated system, or a topological
positional relationship. As an experimental rule for quantitatively
evaluating and predicting these effects on the basis of the acid
dissociation constant of para- and meta-substituted benzoic acid,
there is known Hammett's rule. In the case of the excitation
effect, the electron-withdrawing effect is referred to as the -I
effect, while the electron-donating effect is referred to as the +I
effect, and an atom having higher electronegativity than carbon
exhibits the -I effect. Furthermore, an anion exhibits the +I
effect, while a cation exhibits the -I effect. In the case of the
mesomeric effect, the electron-withdrawing effect is referred to as
the -M effect, while the electron-donating effect is referred to as
the +M effect. Examples of the electron-withdrawing group are shown
below.
Excitation Effect
(-I Effect)
[0100] --O.sup.+R.sub.2>--N.sup.+R.sub.3
[0101] --N.sup.+R.sub.3>--P.sup.+R.sub.3> . . .
[0102] --O.sup.+R.sub.2>--S.sup.+R.sub.2> . . .
[0103] --N.sup.+R.sub.3>--NO.sub.2>--SO.sub.2R>--SOR
[0104] --SO.sub.2R>--SO.sub.3R
[0105] --N.sup.+R.sub.3>--NR.sub.2
[0106] --O.sup.+R.sub.2>--OR
[0107] --S.sup.+R.sub.2>--SR
[0108] --F>--Cl>--Br>--I
[0109] .dbd.O>.dbd.NR>=CR.sub.2
[0110] .dbd.O>--OR
[0111] .ident.N>.ident.CR
[0112] .ident.N>=NR>--NR.sub.2
[0113] --C.ident.CR>--CR.dbd.CR.sub.2>--CR.sub.2CR.sub.3
Mesomeric Effect
(-M Effect)
[0114] .dbd.N.sup.+R.sub.3>.dbd.NR
[0115] .dbd.O>=NR>=CR.sub.2
[0116] .dbd.S>.dbd.O>.ident.N
[0117] Preferred examples of the electron-withdrawing group include
a cyano group, a nitro group, a sulfonyl group, a sulfoxy group, an
acyl group, an alkoxycarbonyl group and a carbamoyl group; more
preferred examples include a cyano group, a nitro group and a
sulfonyl group; and a particularly preferred example is a cyano
group.
[0118] In the present invention, it is preferable that one of
Y.sup.1 and Y.sup.2 is an acidic group and the other is an
electron-attracting group.
[0119] In formula (1), D represents a dye residue. The term "dye
residue" means a group of atoms needed for constituting a dye as a
whole, together with the structure other than D in the formula (1).
Examples of the dye formed by D include polymethine dyes such as
merocyanine, hemicyanine, styryl, oxonol and cyanine;
diarylmethines including acridine, xanthene, and thioxanthene;
triarylmethine, coumarin, indoaniline, indophenol, diazine,
oxazine, thiazine, diketopyrrolopyrrole, indigo, anthraquinone,
perylene, quinacridone, naphthoquinone, bipyridyl, terpyridyl,
tetrapyridyl, and phenanthroline. Preferred examples include
polymethine dyes and polyaryl dyes.
[0120] n represents an integer of 1 or greater, and is preferably 1
to 5, more preferably 1 to 3, and particularly preferably 1.
[0121] In formula (1), L represents a single bond or a divalent
linking group, and L is preferably a divalent linking group. The
divalent linking group is not particularly limited, but is
preferably a divalent linking group having 0 to 30 carbon atoms
(more preferably 1 to 20 carbon atoms). Examples of the divalent
linking group include an alkylene group having 1 to 20 carbon atoms
(preferably an alkylene group having 2 to 10 carbon atoms) and an
arylene group having 6 to 30 carbon atoms (preferably an arylene
group having 6 to 20 carbon atoms). The divalent linking group may
also contain a heteroatom(s), such as nitrogen, sulfur, phosphorus
and oxygen atoms. Preferred examples of L include methylene,
ethylene, propylene, phenylene and ethenylene.
[0122] In the present invention, the dye represented by formula (1)
is a dye represented by any one of formulae (2) to (5). Next, the
dye represented by any one of formulae (2) to (5) will be described
below.
##STR00009##
[0123] In formula (2), Y.sup.1, Y.sup.2, Y.sup.3 and L have the
same meaning as those in formula (1), respectively, and preferable
ranges thereof are also the same.
[0124] LL represents a divalent linking group comprising at least
one selected from the group consisting of an alkenylene group, an
alkynylene group and an arylene group. R.sup.1, R.sup.2 and R.sup.3
each independently represent a hydrogen atom, an aliphatic group,
an aromatic group, or a heterocyclic group linked through a carbon
atom. R.sup.1 and R.sup.2 each may form a ring together with a
substituent(s) present on LL.
[0125] In the present invention, the dye represented by formula (2)
is preferably a dye represented by formula (6).
##STR00010##
[0126] Y.sup.1, Y.sup.2, Y.sup.3, L and R.sup.3 in formula (6) have
the same meaning as those in formula (2), respectively, and
preferable ranges thereof are also the same.
[0127] LL' represents a single bond, or a divalent linking group
comprising at least one selected from the group consisting of an
alkenylene group, an alkynylene group and an arylene group. R.sup.4
represents a hydrogen atom, an aliphatic group, an aromatic group,
or a heterocyclic group linked through a carbon atom. B represents
a group of atoms needed for forming a ring together with the two
carbon atoms and the nitrogen atom on the benzene ring.
##STR00011##
[0128] In formula (3), Y.sup.1, Y.sup.2, Y.sup.3 and L have the
same meaning as those in formula (1), respectively, and preferable
ranges thereof are also the same.
[0129] LL represents a divalent linking group comprising at least
one selected from the group consisting of an alkenylene group, an
alkynylene group and an arylene group. R, R.sup.1, R.sup.2 and
R.sup.3 each independently represent a hydrogen atom, an aliphatic
group, an aromatic group, or a heterocyclic group linked through a
carbon atom. R.sup.1 and R.sup.2 each may form a ring together with
a substituent(s) present on LL.
##STR00012##
[0130] In formula (4), Y.sup.1, Y.sup.2, Y.sup.3 and L have the
same meaning as those in formula (1), respectively, and preferable
ranges thereof are also the same.
[0131] LL represents a divalent linking group comprising at least
one selected from the group consisting of an alkenylene group, an
alkynylene group and an arylene group. R.sup.1, R.sup.2 and R.sup.3
each independently represent a hydrogen atom, an aliphatic group,
an aromatic group, or a heterocyclic group linked through a carbon
atom. R.sup.1 and R.sup.2 each may form a ring together with a
substituent(s) present on LL.
##STR00013##
[0132] In formula (5), Y.sup.1, Y.sup.2, Y.sup.3 and L have the
same meaning as those in formula (1), respectively, and preferable
ranges thereof are also the same.
[0133] LL represents a divalent linking group comprising at least
one selected from the group consisting of an alkenylene group, an
alkynylene group and an arylene group. R.sup.1, R.sup.2 and R.sup.3
each independently represent a hydrogen atom, an aliphatic group,
an aromatic group, or a heterocyclic group linked through a carbon
atom. R.sup.1 and R.sup.2 each may form a ring together with a
substituent(s) present on LL.
[0134] In the present invention, the dye represented by formula (5)
is preferably a dye represented by formula (7).
##STR00014##
[0135] Y.sup.1, Y.sup.2, Y.sup.3, L and R.sup.3 in formula (7) have
the same meaning as those in formula (5), respectively, and
preferable ranges thereof are also the same.
[0136] LL' represents a single bond, or a divalent linking group
comprising at least one selected from the group consisting of an
alkenylene group, an alkynylene group and an arylene group. R.sup.4
represents a hydrogen atom, an aliphatic group, an aromatic group,
or a heterocyclic group linked through a carbon atom. B represents
a group of atoms needed for forming a ring together with the two
carbon atoms and the nitrogen atom on the benzene ring.
[0137] R, R.sup.1, R.sup.2 and R.sup.3 in the formulas (2) to (7)
each independently represent a hydrogen atom, an aliphatic group,
an aromatic group, or a heterocyclic group linked through a carbon
atom. Preferred examples include an aliphatic group and an aromatic
group, and a particularly preferred example is an aliphatic group.
R.sup.3 is preferably a hydrogen atom.
[0138] Examples of the aliphatic group include an alkyl group (e.g.
methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, eicosyl,
2-chloroethyl, 2-cyanoethyl, or 2-ethylhexyl), and a cycloalkyl
group (preferably a substituted or unsubstituted cycloalkyl group
having 3 to 30 carbon atoms, e.g. cyclohexyl, cyclopentyl, or
4-n-dodecylcyclohexyl). Preferred examples of the aliphatic group
include an alkyl group and an alkenyl group, each having 1 to 30
carbon atoms (preferably having 1 to 25 carbon atoms, more
preferably having 1 to 20 carbon atoms) and a cycloalkyl group
having 3 to 50 carbon atoms (preferably having 3 to 30 carbon
atoms), and the aliphatic group may be substituted.
[0139] The aromatic group is preferably a 5- or 6-membered,
substituted or unsubstituted aromatic group having 1 to 30 carbon
atoms (preferably 1 to 20 carbon atoms). Examples of the aromatic
group include a benzene ring, a furan ring, a pyrrole ring, a
pyridine ring, a thiophene ring, an imidazole ring, an oxazole
ring, a thiazole ring, a pyrazole ring, an isoxazole ring, an
isothiazole ring, a pyrimidine ring, a pyrazine ring, or rings
formed by condensation of the foregoing rings. These groups may be
substituted. Preferred examples include a benzene ring, a pyrrole
ring, a pyridine ring and a thiophene ring; more preferred examples
include a benzene ring and a thiophene ring; and a particularly
preferred example is a benzene ring. These groups may be
substituted.
[0140] The heterocyclic group linked through a carbon atom is
preferably a 3- to 6-membered substituted or unsubstituted
heterocyclic group, more preferably a 5- or 6-membered
unsubstituted heterocyclic group, and particularly preferably a
6-membered heterocyclic group (for example, piperidine or
morpholine). These groups may be substituted.
[0141] In formulae (2) to (7), R.sup.1, R.sup.2 and R.sup.4 each
are preferably an alkyl group having 1 to 50 carbon atoms
(preferably 1 to 25 carbon atoms), an alkoxy group having 1 to 50
carbon atoms (preferably 1 to 25 carbon atoms), an alkylthio group
having 1 to 50 carbon atoms (preferably 1 to 25 carbon atoms), a
cycloalkyl group having 3 to 50 carbon atoms (preferably having 3
to 30 carbon atoms), an aryl group having 6 to 50 carbon atoms
(preferably 6 to 30 carbon atoms), an aryloxy group having 6 to 50
carbon atoms (preferably 6 to 30 carbon atoms), an arylthio group
having 6 to 50 carbon atoms (preferably 6 to 30 carbon atoms), and
a 3- to 10-membered (preferably 5- to 7-membered) heterocyclic ring
having 1 to 30 carbon atoms (preferably 1 to 20 carbon atoms).
Preferred examples include an alkyl group having 1 to 25 carbon
atoms (for example, methyl, ethyl, n-butyl, n-hexyl, isobutyl,
sec-butyl, t-butyl, n-dodecyl, cyclohexyl, or benzyl), a cycloalkyl
group having 3 to 50 carbon atoms (preferably having 3 to 30 carbon
atoms), an aryl group having 6 to 30 carbon atoms (for example,
phenyl, tolyl, or naphthyl), and an alkoxy group having 1 to 25
carbon atoms (for example, methoxy, ethoxy, isopropoxy or
butoxy).
[0142] In formulae (2) to (7), R.sup.3 is preferably a hydrogen
atom, an alkyl group having 1 to 50 carbon atoms (preferably 1 to
25 carbon atoms), a cycloalkyl group having 3 to 50 carbon atoms
(preferably having 3 to 30 carbon atoms), an aryl group having 6 to
50 carbon atoms (preferably 6 to 30 carbon atoms) and a 3- to
10-membered (preferably 5- to 7-membered) heterocyclic ring having
1 to 30 carbon atoms (preferably 1 to 20 carbon atoms); and more
preferably a hydrogen atom.
[0143] In formulae (3), (5) and (7), R is preferably an alkyl group
having 1 to 50 carbon atoms (preferably 1 to 25 carbon atoms), a
cycloalkyl group having 3 to 50 carbon atoms (preferably having 3
to 30 carbon atoms), an aryl group having 6 to 50 carbon atoms
(preferably 6 to 30 carbon atoms), or a 3- to 10-membered
(preferably 5- to 7-membered) heterocyclic ring having 1 to 30
carbon atoms (preferably 1 to 20 carbon atoms); and more preferably
an alkyl group having 1 to 25 carbon atoms, a cycloalkyl group
having 3 to 30 carbon atoms or an aryl group having 6 to 30 carbon
atoms.
[0144] In the formulas (2) to (5), LL represents a divalent linking
group comprising at least one selected from the group consisting of
an alkenylene group, an alkynylene group and an arylene group. LL
may be a combination of these groups, and may also be
substituted.
[0145] The alkenylene group is preferably an alkenylene group
having 2 to 30 carbon atoms (preferably 2 to 10 carbon atoms).
Preferred examples thereof include ethenylene. The alkynylene group
is preferably an alkynylene group having 2 to 30 carbon atoms
(preferably 2 to 10 carbon atoms). Preferred examples thereof
include ethynylene. The arylene group includes an aromatic
hydrocarbon ring group and an aromatic heterocycle group, and is
preferably an arylene group having 6 to 50 carbon atoms (preferably
6 to 30 carbon atoms). Preferred examples of the arylene group
include a benzene ring, a furan ring, a pyrrole ring and a
thiophene ring, or divalent rings formed by condensation of the
foregoing rings.
[0146] In the formulas (2) to (5), LL is preferably an alkenylene
group, an alkynylene group, an arylene group or a divalent linking
group of combination of these groups.
[0147] Examples of LL include those groups represented by any one
of the formulas shown below. Among the formulas shown below, L-a,
L-b, L-c or L-e is preferable; L-a, L-b or L-e is more preferable;
and L-b is particularly preferable.
##STR00015##
[0148] In the formulas (6) and (7), LL' represents a single bond,
or a divalent linking group comprising at least one selected from
the group consisting of an alkenylene group, an alkynylene group
and an arylene group. In the formulas (6) and (7), the divalent
linking group represented by LL' has the same meaning as that of LL
in formulae (2) to (5), and a preferable range thereof is also the
same.
[0149] In the formulas (6) and (7), LL' is preferably a single
bond, an alkenylene group, an alkynylene group, an arylene group or
a divalent linking group of combination of these groups; and more
preferably an alkenylene group, an alkynylene group, an arylene
group or a divalent linking group of combination of these
groups.
[0150] In the formulas (6) and (7), B represents a group of atoms
needed for forming a ring together with the two carbon atoms and
the nitrogen atom on the benzene ring.
[0151] Examples of the ring formed by B include dihydropyrrole,
tetrahydropyridine, dihydroazepine, dihydrothiazole,
dihydroimidazole, dihydrooxazole, tetrahydropyradine,
tetrahydropyrimidine, tetrahydropyridadine, and coumarine. These
rings can be substituted with a group(s) represented by the
substituent W described below, or condensed with other ring(s) such
as benzene ring and herterocycles. The ring formed by B is
preferably a substituted or nonsubstituted dihydropyrrole, a
substituted or nonsubstituted tetrahydropyridine, a substituted or
nonsubstituted tetrahydropyradine, or a substituted or
nonsubstituted dihydroazepine; and more preferably a substituted or
nonsubstituted dihydropyrrole, a substituted or nonsubstituted
tetrahydropyridine, or a substituted or nonsubstituted
dihydroazepine.
[0152] The acidic group (for example, a carboxyl group, a
phosphonic acid group or a sulfo group) in formulas (1) to (7) may
be dissociated and have a counter cation. The counter cation is not
particularly limited, and may be any of an organic cation and an
inorganic cation. Representative examples include an alkali metal
ion (lithium, sodium, potassium, or the like), an alkaline earth
metal ion (magnesium, calcium or the like), and cations of
ammonium, alkylammonium (for example, diethylammonium, or
tetrabutylammonium), pyridinium, alkylpyridinium (for example,
methylpyridinium), guanidium and tetraalkylphosphonium.
(Optional Substituent)
[0153] According to the present invention, the compound may have an
appropriate substituent (hereinafter, referred to as substituent
W). Specific examples of the substituent W include: a halogen atom
(e.g. a fluorine atom, a chlorine atom, a bromine atom, or an
iodine atom); an alkyl group [which represents a substituted or
unsubstituted linear, branched, or cyclic alkyl group, and which
includes an alkyl group (preferably an alkyl group having 1 to 30
carbon atoms, e.g. a methyl group, an ethyl group, an n-propyl
group, an isopropyl group, a t-butyl group, an n-octyl group, an
eicosyl group, a 2-chloroethyl group, a 2-cyanoethyl group, or a
2-ethylhexyl group), a cycloalkyl group (preferably a substituted
or unsubstituted cycloalkyl group having 3 to 30 carbon atoms, e.g.
a cyclohexyl group, a cyclopentyl group, or a 4-n-dodecylcyclohexyl
group), a bicycloalkyl group (preferably a substituted or
unsubstituted bicycloalkyl group having 5 to 30 carbon atoms, i.e.
a monovalent group obtained by removing one hydrogen atom from a
bicycloalkane having 5 to 30 carbon atoms, e.g. a
bicyclo[1.2.2]heptan-2-yl group or a bicyclo[2.2.2]octan-3-yl
group), and a tricyclo or higher structure having three or more
ring structures; and an alkyl group in substituents described below
(e.g. an alkyl group in an alkylthio group) represents such an
alkyl group of the above concept]; an alkenyl group [which
represents a substituted or unsubstituted linear, branched, or
cyclic alkenyl group, and which includes an alkenyl group
(preferably a substituted or unsubstituted alkenyl group having 2
to 30 carbon atoms, e.g. a vinyl group, an allyl group, a prenyl
group, a geranyl group, or an oleyl group), a cycloalkenyl group
(preferably a substituted or unsubstituted cycloalkenyl group
having 3 to 30 carbon atoms, i.e. a monovalent group obtained by
removing one hydrogen atom from a cycloalkene having 3 to 30 carbon
atoms, e.g. a 2-cyclopenten-1-yl group or a 2-cyclohexen-1-yl
group), and a bicycloalkenyl group (which represents a substituted
or unsubstituted bicycloalkenyl group, preferably a substituted or
unsubstituted bicycloalkenyl group having 5 to 30 carbon atoms,
i.e. a monovalent group obtained by removing one hydrogen atom from
a bicycloalkene having one double bond, e.g. a
bicyclo[2.2.1]hept-2-en-1-yl group or a bicyclo[2.2.2]oct-2-en-4-yl
group)]; an alkynyl group (preferably a substituted or
unsubstituted alkynyl group having 2 to 30 carbon atoms, e.g. an
ethynyl group, a propargyl group, or a trimethylsilylethynyl
group); an aryl group (preferably a substituted or unsubstituted
aryl group having 6 to 30 carbon atoms, e.g. a phenyl group, a
p-tolyl group, a naphthyl group, an m-chlorophenyl group, or an
o-hexadecanoylaminophenyl group); an aromatic group (e.g. a benzene
ring, a furan ring, a pyrrole ring, a pyridine ring, a thiophene
ring, an imidazole ring, an oxazole ring, a thiazole ring, a
pyrazole ring, an isoxazole ring, an isothiazole ring, a pyrimidine
ring, a pyrazine ring, or rings formed by condensation of the
foregoing rings); a heterocyclic group (preferably a monovalent
group obtained by removing one hydrogen atom from a substituted or
unsubstituted 5- or 6-membered aromatic or nonaromatic heterocyclic
compound; more preferably a 5- or 6-membered aromatic heterocyclic
group having 3 to 30 carbon atoms, e.g. a 2-furyl group, a
2-thienyl group, a 2-pyrimidinyl group, a 2-benzothiazolyl group);
a cyano group; a hydroxyl group; a nitro group; a carboxyl group;
an alkoxy group (preferably a substituted or unsubstituted alkoxy
group having 1 to 30 carbon atoms, e.g. a methoxy group, an ethoxy
group, an isopropoxy group, a t-butoxy group, an n-octyloxy group,
or a 2-methoxyethoxy group); an aryloxy group (preferably a
substituted or unsubstituted aryloxy group having 6 to 30 carbon
atoms, e.g. a phenoxy group, a 2-methylphenoxy group, a
4-t-butylphenoxy group, a 3-nitrophenoxy group, or a
2-tetradecanoylaminophenoxy group); a silyloxy group (preferably a
silyloxy group having 3 to 20 carbon atoms, e.g. a
trimethylsilyloxy group or a t-butyldimethylsilyloxy group); a
heterocyclic oxy group (preferably a substituted or unsubstituted
heterocyclic oxy group having 2 to 30 carbon atoms, e.g. a
1-phenyltetrazol-5-oxy group or a 2-tetrahydropyranyloxy group); an
acyloxy group (preferably a formyloxy group, a substituted or
unsubstituted alkylcarbonyloxy group having 2 to 30 carbon atoms,
or a substituted or unsubstituted arylcarbonyloxy group having 7 to
30 carbon atoms, e.g. a formyloxy group, an acetyloxy group, a
pivaloyloxy group, a stearoyloxy group, a benzoyloxy group, or a
p-methoxyphenylcarbonyloxy group); a carbamoyloxy group (preferably
a substituted or unsubstituted carbamoyloxy group having 1 to 30
carbon atoms, e.g. an N,N-dimethylcarbamoyloxy group, an
N,N-diethylcarbamoyloxy group, a morpholinocarbonyloxy group, an
N,N-di-n-octylaminocarbonyloxy group, or an N-n-octylcarbamoyloxy
group); an alkoxycarbonyloxy group (preferably a substituted or
unsubstituted alkoxycarbonyloxy group having 2 to 30 carbon atoms,
e.g. a methoxycarbonyloxy group, an ethoxycarbonyloxy group, a
t-butoxycarbonyloxy group, or an n-octylcarbonyloxy group); an
aryloxycarbonyloxy group (preferably a substituted or unsubstituted
aryloxycarbonyloxy group having 7 to 30 carbon atoms, e.g. a
phenoxycarbonyloxy group, a p-methoxyphenoxycarbonyloxy group, or a
p-n-hexadecyloxyphenoxycarbonyloxy group); an amino group
(preferably an amino group, a substituted or unsubstituted
alkylamino group having 1 to 30 carbon atoms, or a substituted or
unsubstituted arylamino group having 6 to 30 carbon atoms, e.g. an
amino group, a methylamino group, a dimethylamino group, an anilino
group, an N-methyl-anilino group, or a diphenylamino group); an
acylamino group (preferably a formylamino group, a substituted or
unsubstituted alkylcarbonylamino group having 1 to 30 carbon atoms,
or a substituted or unsubstituted arylcarbonylamino group having 6
to 30 carbon atoms, e.g. a formylamino group, an acetylamino group,
a pivaloylamino group, a lauroylamino group, a benzoylamino group,
or a 3,4,5-tri-n-octyloxyphenylcarbonylamino group); an
aminocarbonylamino group (preferably a substituted or unsubstituted
aminocarbonylamino group having 1 to 30 carbon atoms, e.g. a
carbamoylamino group, an N,N-dimethylaminocarbonylamino group, an
N,N-diethylaminocarbonylamino group, or a morpholinocarbonylamino
group); an alkoxycarbonylamino group (preferably a substituted or
unsubstituted alkoxycarbonylamino group having 2 to 30 carbon
atoms, e.g. a methoxycarbonylamino group, an ethoxycarbonylamino
group, a t-butoxycarbonylamino group, an
n-octadecyloxycarbonylamino group, or an
N-methyl-methoxycarbonylamino group); an aryloxycarbonylamino group
(preferably a substituted or unsubstituted aryloxycarbonylamino
group having 7 to 30 carbon atoms, e.g. a phenoxycarbonylamino
group, a p-chlorophenoxycarbonylamino group, or an
m-n-octyloxyphenoxycarbonylamino group); a sulfamoylamino group
(preferably a substituted or unsubstituted sulfamoylamino group
having 0 to 30 carbon atoms, e.g. a sulfamoylamino group, an
N,N-dimethylaminosulfonylamino group, or an
N-n-octylaminosulfonylamino group); an alkyl- or aryl-sulfonylamino
group (preferably a substituted or unsubstituted alkylsulfonylamino
group having 1 to 30 carbon atoms, or a substituted or
unsubstituted arylsulfonylamino group having 6 to 30 carbon atoms,
e.g. a methylsulfonylamino group, a butylsulfonylamino group, a
phenylsulfonylamino group, a 2,3,5-trichlorophenylsulfonylamino
group, or a p-methylphenylsulfonylamino group); a mercapto group;
an alkylthio group (preferably a substituted or unsubstituted
alkylthio group having 1 to 30 carbon atoms, e.g. a methylthio
group, an ethylthio group, or an n-hexadecylthio group); an
arylthio group (preferably a substituted or unsubstituted arylthio
group having 6 to 30 carbon atoms, e.g. a phenylthio group, a
p-chlorophenylthio group, or an m-methoxyphenylthio group); a
heterocyclic thio group (preferably a substituted or unsubstituted
heterocyclic thio group having 2 to 30 carbon atoms, e.g. a
2-benzothiazolylthio group or a 1-phenyltetrazol-5-ylthio group); a
sulfamoyl group (preferably a substituted or unsubstituted
sulfamoyl group having 0 to 30 carbon atoms, e.g. an
N-ethylsulfamoyl group, an N-(3-dodecyloxypropyl)sulfamoyl group,
an N,N-dimethylsulfamoyl group, an N-acetylsulfamoyl group, an
N-benzoylsulfamoyl group, or an N--(N'-phenylcarbamoyl)sulfamoyl
group); a sulfo group; an alkyl- or aryl-sulfinyl group (preferably
a substituted or unsubstituted alkylsulfinyl group having 1 to 30
carbon atoms, or a substituted or unsubstituted arylsulfinyl group
having 6 to 30 carbon atoms, e.g. a methylsulfinyl group, an
ethylsulfinyl group, a phenylsulfinyl group, or a
p-methylphenylsulfinyl group); an alkyl- or aryl-sulfonyl group
(preferably a substituted or unsubstituted alkylsulfonyl group
having 1 to 30 carbon atoms, or a substituted or unsubstituted
arylsulfonyl group having 6 to 30 carbon atoms, e.g. a
methylsulfonyl group, an ethylsulfonyl group, a phenylsulfonyl
group, or a p-methylphenylsulfonyl group); an acyl group
(preferably a formyl group, a substituted or unsubstituted
alkylcarbonyl group having 2 to 30 carbon atoms, a substituted or
unsubstituted arylcarbonyl group having 7 to 30 carbon atoms, or a
substituted or unsubstituted heterocyclic carbonyl group having 4
to 30 carbon atoms, which is bonded to said carbonyl group through
a carbon atom, e.g. an acetyl group, a pivaloyl group, a
2-chloroacetyl group, a stearoyl group, a benzoyl group, a
p-n-octyloxyphenylcarbonyl group, a 2-pyridylcarbonyl group, or a
2-furylcarbonyl group); an aryloxycarbonyl group (preferably a
substituted or unsubstituted aryloxycarbonyl group having 7 to 30
carbon atoms, e.g. a phenoxycarbonyl group, an
o-chlorophenoxycarbonyl group, an m-nitrophenoxycarbonyl group, or
a p-t-butylphenoxycarbonyl group); an alkoxycarbonyl group
(preferably a substituted or unsubstituted alkoxycarbonyl group
having 2 to 30 carbon atoms, e.g. a methoxycarbonyl group, an
ethoxycarbonyl group, a t-butoxycarbonyl group, or an
n-octadecyloxycarbonyl group); a carbamoyl group (preferably a
substituted or unsubstituted carbamoyl group having 1 to 30 carbon
atoms, e.g. a carbamoyl group, an N-methylcarbamoyl group, an
N,N-dimethylcarbamoyl group, an N,N-di-n-octylcarbamoyl group, or
an N-(methylsulfonyl)carbamoyl group); an aryl- or heterocyclic-azo
group (preferably a substituted or unsubstituted aryl azo group
having 6 to 30 carbon atoms, or a substituted or unsubstituted
heterocyclic azo group having 3 to 30 carbon atoms, e.g. a
phenylazo group, a p-chlorophenylazo group, or a
5-ethylthio-1,3,4-thiadiazol-2-ylazo group); an imido group
(preferably an N-succinimido group or an N-phthalimido group); a
phosphino group (preferably a substituted or unsubstituted
phosphino group having 2 to 30 carbon atoms, e.g. a
dimethylphosphino group, a diphenylphosphino group, or a
methylphenoxyphosphino group); a phosphinyl group (preferably a
substituted or unsubstituted phosphinyl group having 2 to 30 carbon
atoms, e.g. a phosphinyl group, a dioctyloxyphosphinyl group, or a
diethoxyphosphinyl group); a phosphinyloxy group (preferably a
substituted or unsubstituted phosphinyloxy group having 2 to 30
carbon atoms, e.g. a diphenoxyphosphinyloxy group or a
dioctyloxyphosphinyloxy group); a phosphinylamino group (preferably
a substituted or unsubstituted phosphinylamino group having 2 to 30
carbon atoms, e.g. a dimethoxyphosphinylamino group or a
dimethylaminophosphinylamino group); and a silyl group (preferably
a substituted or unsubstituted silyl group having 3 to 30 carbon
atoms, e.g. a trimethylsilyl group, a t-butyldimethylsilyl group,
or a phenyldimethylsilyl group).
[0154] The substituent may be further substituted. In that case,
examples of the substituent include the substituent W mentioned
above.
[0155] Specific examples of the dye having at least one structure
represented by any one of formulas (1) to (7) are shown in the
followings, but the present invention is not limited thereto.
##STR00016## ##STR00017## ##STR00018## ##STR00019##
##STR00020##
[0156] The dye (dye compound) represented by any one of formulae
(1) to (7) can be synthesized by, for example, methods described or
cited in F. M. Harmer, "Heterocyclic Compounds--Cyanine Dyes and
Related Compounds", John Wiley & Sons, New York and London,
1994, or methods similar thereto.
[0157] In order to adsorb a dye to semiconductor fine particles, it
is preferable to immerse semiconductor fine particles that have
been thoroughly dried, in a dye solution for dye adsorption formed
from a solvent and the dye for use in the present invention. In
regard to the solvent that is used in the dye solution for dye
adsorption, any solvent capable of dissolving the dye for use in
the present invention can be used without any particular
limitation. For example, ethanol methanol, isopropanol, toluene,
t-butanol, acetonitrile, acetone or n-butanol can be used. Among
them, ethanol and toluene can be preferably used.
[0158] The dye solution for dye adsorption formed from a solvent
and the dye for use in the present invention may be heated if
necessary, at 50.degree. C. to 100.degree. C. Adsorption of the dye
may be carried out before or after the process of applying the
semiconductor fine particles. Adsorption of the dye may also be
conducted by simultaneously applying the semiconductor fine
particles and the dye. Any unadsorbed dye is removed by washing. In
the case of performing calcination of the coating film, it is
preferable to carry out the adsorption of the dye after
calcination. After calcination has been performed, it is
particularly preferable to perform the adsorption of the dye
rapidly before water adsorbs to the surface of the coating film.
The dye to be adsorbed may be composed of a single kind, or a
mixture of plural kinds of dyes may also be used. In the case of
using a mixture, two or more kinds of the dye for use in the
present invention may be mixed, or the dye for use in the present
invention may be mixed with a complex dye described in U.S. Pat.
No. 4,927,721, U.S. Pat. No. 4,684,537, U.S. Pat. No. 5,084,365,
U.S. Pat. No. 5,350,644, U.S. Pat. No. 5,463,057, U.S. Pat. No.
5,525,440, and JP-A-7-249790. The dyes are selected so that the
wavelength region for photoelectric conversion can be made as broad
as possible when the dyes are mixed. In the case of using a mixture
of dyes, it is required to prepare a dye solution for dye
adsorption by dissolving all of the dyes used therein.
[0159] The overall amount of use of the dye is preferably 0.01 to
100 millimoles, more preferably 0.1 to 50 millimoles, and
particularly preferably 0.1 to 10 millimoles, per square meter of
the support. In this case, the amount of use of the dye for use in
the present invention is preferably adjusted to 5% by mole or
more.
[0160] The amount of the dye adsorbed to the semiconductor fine
particles is preferably 0.001 to 1 millimole, and more preferably
0.1 to 0.5 millimoles, based on 1 g of the semiconductor fine
particles.
[0161] When the amount of the dye is adjusted to such a range, the
sensitization effect for the semiconductor can be sufficiently
obtained. On the other hand, if the amount of the dye is too
smaller, the sensitization effect is insufficient, and if the
amount of the dye is excessive, the portion of the dye that is not
attached to the semiconductor is suspended, and causes a decrease
in the sensitization effect.
[0162] For the purpose of reducing the interaction between dye
molecules such as association, a colorless compound may be
co-adsorbed. Examples of the hydrophobic compound that is
co-adsorbed include steroid compounds having a carboxyl group (for
example, cholic acid and pivaloyl acid).
[0163] After the dye has been adsorbed, the surface of the
semiconductor fine particles may be treated using amines. Preferred
examples of the amines include 4-tert-butylpyridine, and
polyvinylpyridine. These may be used directly when the compounds
are liquids, or may be used in a state of being dissolved in an
organic solvent.
[0164] Hereinafter, the charge transfer layer and the counter
electrode will be explained in detail.
[0165] The charge transfer layer is a layer having a function of
supplementing electrons to an oxidant of the dye, and is provided
between the light-receiving electrode and the counter electrode.
Representative examples of the material forming the charge transfer
layer include a liquid prepared by dissolving a redox pair in an
organic solvent, a so-called gel electrolyte obtained by
impregnating a polymer matrix with a liquid prepared by dissolving
a redox pair in an organic solvent, and a molten salt containing a
redox pair.
[0166] Examples of the redox pair include a combination of iodine
and an iodide (for example, lithium iodide, tetrabutylammonium
iodide, or tetrapropylammonium iodide), a combination of an
alkylviologen (for example, methylviologen chloride, hexylviologen
bromide, or benzylviologen tetrafluoroborate) and a reductant
thereof, a combination of a polyhydroxybenzene (for example,
hydroquinone or naphthohydroquinone) and an oxidant thereof, and a
combination of a divalent iron complex and a trivalent iron complex
(for example, potassium ferricyanide and potassium ferrocyanide).
Among these, a combination of iodine and an iodide is preferred.
Examples of the organic solvent that dissolves these materials
include aprotic polar solvents (for example, acetonitrile,
propylene carbonate, ethylene carbonate, dimethylformamide,
dimethylsulfoxide, sulfolane, 1,3-dimethylimidazolinone, and
3-methyloxazolidinone); the water-containing electrolyte liquid
described in JP-A-2002-110262; and the electrolyte solvents
described in JP-A-2000-36332, JP-A-2000-243134 and WO 00/54361.
Among these, preferred organic solvents are acetonitrile,
methoxypropionitrile, propylene carbonate and
.gamma.-butyrolactone.
[0167] Examples of the additives that are added to the electrolyte
include 4-tert-butylpyridine mentioned above, as well as the
pyridine and pyridine-based compounds described in
JP-A-2003-331986; the aminopyridine-based compounds described in
JP-A-2004-47229, JP-A-2004-171821 and the like; the
benzimidazole-based compounds described in JP-A-2004-273272; the
aminotriazole-based compounds and aminothiazole-basd compounds
described in JP-A-2005-38711; the imidazole-based compounds
described in JP-A-2005-108663; quinoline-based compounds (see, for
example, JP-A-2005-135782); aminotriazine-based compounds (see, for
example, JP-A-2005-183166); urea derivatives (see, for example,
JP-A-2003-168493); amide compounds (see, for example,
JP-A-2004-103404); pyrimidine-based compounds (see, for example,
JP-A-2004-247158); and heterocycles that do not contain nitrogen
(see, for example, JP-A-2005L166612, JP-A-2005-166613 and
JP-A-2005-16615).
[0168] It is also preferable to employ a method of controlling the
water content of the electrolyte liquid, in order to enhance the
efficiency. Preferred examples of the method of controlling the
water content include a method of controlling the concentration
(see, for example, JP-A-2000-323189 and JP-A-2001-76774), and a
method of adding a dehydrating agent (see, for example,
JP-A-2002-237335).
[0169] In order to reduce the toxicity of iodine, a clathrate
compound of iodine with cyclodextrin may be used as described in
JP-A-2004-235011. Alternatively, a method of supplying moisture on
a steady basis may be used as described in JP-A-2003-25709.
Furthermore, a cyclic amidine may be used as described in Japanese
Patent No. 3462115; or an oxidation inhibitor (see, for example,
JP-A-2004-39292), a hydrolysis inhibitor (see, for example,
JP-A-2004-111276), a decomposition inhibitor (see, for example,
JP-A-2004-111277) or zinc iodide (see, for example,
JP-A-2004-152613) may be added.
[0170] A molten salt may also be used as the electrolyte, and
preferred examples of the molten salt include an ionic liquid
containing an imidazolium or triazolium type cation (see, for
example, JP-T-9-507334, JP-A-8-259543, JP-A-2003-31270,
JP-A-2005-112733, JP-A-2005-116367, JP-A-2005-112733,
JP-A-2003-68374, JPA-2003-92153, JP-A-2004-241378, JP-A-2005-85587
and JP-A-2004-87387); an oxazolium-based salt (see, for example,
JP-A-2000-53662); a pyridinium-based salt (see, for example,
JP-A-2000-58891, JP-A-2001-23705, JP-A-2001-167630,
JP-A-2001-256828, and JP-A-2001-266962); a guanidium-based salt
(see, for example, JP-A-2001-35253); and combinations of these
(see, for example, JP-A-2000-90991 and JP-A-2001-35552). These
cations may be used in combination with particular anions, and
examples of the anions are those described in JP-A-2002-75442,
JP-A-2001-75443, JP-A-2002-170426, JP-A-2002-298913,
JP-A-2002-367426, JP-A-2003-17148 and the like. Additives may be
added these molten salts, and preferred examples of the additives
include those described in JP-A-2001-67931, JP-A-2001-160427,
JP-A-2002-289267, JPA-2002-289268, JP-A-2000-90991,
JP-A-2000-100485, JP-A-2001-283943, and the like. As described in
JP-A-2002-319314 or JP-A-2002-343440, the molten salt may have a
substituent having liquid crystalline properties. Furthermore, the
quaternary ammonium salt-based molten salt described in
JP-A-2005-104845, JP-A-2005-104846, JPA-2005-179254 and the like
may also be used.
[0171] Molten salts other than those described above include, for
example, the molten salts described in JP-A-2005-139100 and
JP-A-2005-145927, as well as a molten salt to which fluidity at
room temperature has been imparted by mixing lithium iodide and at
least one kind of other lithium salt (for example, lithium acetate
or lithium perchlorate) with polyethylene oxide. The amount of
addition of the polymer in this case is 1 to 50% by mass.
Furthermore, the electrolyte liquid may contain
.gamma.-butyrolactone, and this .gamma.-butyrolactone increases the
diffusion efficiency of iodide ions, and thereby, the conversion
efficiency is enhanced.
[0172] The electrolyte may be quasi-solidified by adding a gelling
agent to an electrolyte liquid formed from an electrolyte and a
solvent, and gelling the electrolyte liquid thereby. Examples of
the gelling agent include an organic compound having a molecular
weight of 1000 or less (see, for example, JP-A-11-185836,
JP-A-2000-36608 and JP-A-2000-58140); an Si-containing compound
having a molecular weight in the range of 500 to 5000 (see, for
example, JP-A-2003-203520); an organic salt obtained from a
particular acidic compound and a particular basic compound (see,
for example, JP-A-2003-203520); a sorbitol derivative (see, for
example, JP-A-2003-346928); and polyvinylpyridine (see, for
example, JP-A-2004-227920 and JP-A-2005-93370).
[0173] Furthermore, a method of confining a matrix polymer, a
crosslinked type polymer compound or monomer, a crosslinking agent,
an electrolyte and a solvent, in a polymer may be used.
[0174] Preferred examples of the matrix polymer include a polymer
having a nitrogen-containing heterocyclic ring in a repeating unit
in the main chain or in a side chain, and a crosslinked structure
formed by reacting the polymer with an electrophilic compound (see,
for example, JP-A-11-12691 and JP-A-2000-86724); a polymer having a
triazine structure and a polymer having a ureide structure (see,
for example, JP-A-2000-251532); a polymer containing a liquid
crystalline compound (see, for example; JP-A-2000-319260 and
JP-A-2002-246066), a polymer having an ether bond (see, for
example, JP-A-2000-150006, JP-A-2002-63813, JP-A-2001-338700, and
JPA-2002-75480); a polyvinylidene fluoride-based polymer (see, for
example, JP-A-2003-303628); a methacrylate/acrylate-based polymer
(see, for example, JP-A-2001-28276 and JP-A-2001-210390); a
thermosetting resin (see, for example,'JP-A-2002-363414 and
JP-A-2002-305041); crosslinked polysiloxane (see, for example,
JPA-2002-216861); polyvinyl alcohol (PVA) (see, for example,
JP-A-2002-175841); a clathrate compound of polyalkylene glycol and
dextrin (see, for example, JP-A-2004-327271); a system incorporated
with an oxygen-containing or sulfur-containing polymer (see, for
example, JP-A-2005-108845); and a naturally occurring polymer (see,
for example, JP-A-2005-71688). An alkali-swellable polymer (see,
for example, JP-A-2002-175482), a polymer having a component
capable of forming a charge transfer complex with a cation moiety
and iodine within one polymer molecule (see, for example,
JPA-2005-63791), or the like may be added to those matrix
polymers.
[0175] A system containing, as a matrix polymer, a crosslinked
polymer formed by reacting a bifunctional or higher-functional
isocyanate as one component with a functional group such as a
hydroxyl group, an amino group or a carboxyl group, may also be
used. Examples of this system are described in JP-A-2000-228234,
JPA-2002-184478, JP-A-2002-289271 and JP-A-2003-303630.
Furthermore, a crosslinked polymer based on a hydrosilyl group and
a double-bonded compound (see, for example, JP-A-2003-59548), a
crosslinking method involving reacting polysulfonic acid,
polycarboxylic acid or the like with a divalent or higher-valent
metal ion compound (see, for example, JP-A-2003-86258), and the
like may also be used.
[0176] Examples of the solvent that can be used with preference in
combintion with the quasi-solid electrolyte described above,
include particular phosphates (see, for example, JP-A-2000-100486
and JP-A-2003-16833); a mixed solvent containing ethylene carbonate
(see, for example, JP-A-2004-87202); a solvent having a particular
relative permittivity (see, for example, JP-A-2004-335366); and the
solvents described in JP-A-2003-16833 and JP-A-2003-264011.
[0177] A liquid electrolyte solution may be retained in a solid
electrolyte membrane or in pores, and preferred examples of the
method include the usage of an electrically conductive polymer
membrane (JP-A-11-339866), a fibrous solid (JP-A-2000-357544), and
a fabric-like solid such as filter (JP-A-2001-345125). It is also
acceptable to use the particular combination of a gel electrolyte
and an electroconductive resin counter electrode described in
JP-A-2003-157914.
[0178] A solid charge transport system such as a p-type
semiconductor or a hole transporting material may also be used
instead of the liquid electrolytes and quasi-solid electrolytes
described above. Preferred examples of the p-type semiconductor
include CuI (see, for example, JP-A-2001-156314, JP-A-2001-185743,
JP-A-2001-185743, JP-A-2001-230434, JP-A-2003-273381,
JP-A-2003-234485, JP-A-2003-243681, and JP-A-2003-234486), CuSCN
and p-SbAl (see, for example, JP-A-2003-258284). Preferred examples
of the producing method of the hole transporting material include
those described in, for example, JP-A-2003-331938,
JP-A-2001-168359, JP-A-2001-196612, JP-A-2001-257370,
JP-A-2002-246623, JP-A-2002-246624, and JP-A-2003-289151.
[0179] A photoelectrochemical cell having high conversion
efficiency can be obtained by using a laminate in which a hole
transporter is provided adjacent to a photosensitive layer of the
semiconductor fine particles having the dye used in the present
invention adsorbed thereto. The hole transporter is not
particularly limited, but an organic hole transporting material can
be used. Preferred examples of the hole transporter include
electrically conductive polymers such as polythiophene (see, for
example, JPA-2000-106223 and JP-A-2003-364304), polyaniline (see,
for example, JP-A-2003-264304), polypyrrole (see, for example,
JP-A-2000-106224 and JP-A-2003-264304), and polysilane (see, for
example, JP-A-2001-53555 and JP-A-2001-203377); a Spiro compound in
which two rings share a central element adopting a tetrahedral
structure, such as C and Si (see, for example, JP-T-11-513522 and
JP-T-2001-525108); aromatic amine derivatives such as triarylamine
(see, for example, JP-A-11-144773, JP-A-11-339868,
JP-A-2003-123856, JP-A-2003-197942 and JP-A-2004-356281);
triphenylene derivatives (see, for example, JP-A-11-176489);
nitrogen-containing heterocycle derivatives (see, for example,
JP-A-2001-85077 and JP-A-2001-85713); and liquid crystalline cyano
derivatives (see, for example, Japanese Patent No. 3505381).
[0180] The redox pair serves as a carrier for electrons, and thus
is required at a certain concentration. A preferred overall
concentration is 0.01 moles/liter or more, more preferably 0.1
moles/liter or more, and particularly preferably 0.3 moles/liter or
more. In this case, the upper limit of the concentration is not
particularly limited, but is usually about 5 moles/liter.
[0181] The counter electrode is an electrode working as a positive
electrode in the photoelectrochemical cell. The counter electrode
usually has the same meaning as the electrically conductive support
described above, but in a construction which is likely to maintain
a sufficient strength, a support is not necessarily required.
However, a construction having a support is advantageous in terms
of sealability. Examples of the material for the counter electrode
include platinum, carbon, and electrically conductive polymers.
Preferred examples include platinum (see, for example,
JP-A-2001-102102), carbon (see, for example, JP-A-2002-298936,
JP-A-2003-297446, JP-A-2004-127849, JP-A-2004-152747,
JP-A-2004-165015, JP-A-2004-111216, JP-A-2004-241228, and
JP-A-2004-319872), and electrically conductive polymers (see, for
example, JP-A-2003-317814, JP-A-2004-319131, and JP-A-2005-116301).
Materials described in JP-A-2001-43908, JP-A-2003-142168,
JP-A-2004-127849 and JP-A-2004-152747 may also be used.
[0182] A preferred structure of the counter electrode is a
structure having a high charge collecting effect. Preferred
examples thereof include those described in, for example,
JP-A-10-505192, JP-A-2004-296669, JP-A-2005-11609,
JP-A-2005-141996, JP-A-2005-142090, JP-A-2005-158470,
JP-A-2000-348784, JP-A-2005-158379, JP-A-2000-294305,
JP-A-2001-243995, JP-A-2004-241228, JP-A-2004-296203,
JP-A-2004-319872, and JP-A-2005-197097.
[0183] In regard to the light-receiving electrode, a composite
electrode of titanium oxide and tin oxide (TiO.sub.2/SnO.sub.2) or
the like may be used. Examples of mixed electrodes of titania
include those described in JP-A-2000-113913, JP-A-2004-95387,
JPA-2001-155791, JP-A-2003-272723, JP-A-05-504023,
JP-A-2000-114563, JP-A-2002-75476, JP-A-2002-8741, CN 1350334(A),
JP-A-2003-272724, JP-A-2003-308891, JP-A-2005-174934,
JP-A-2001-358348, JP-A-2003-123862, JP-A-2004-103420,
JP-A-2005-39013 and JP-A-2003-317815. Examples of mixed electrodes
of materials other than titania include those described in
JP-A-2001-185243, JP-A-2003-282164, JP-A-2003-289151,
JP-A-2003-321299, JP-A-2002-93471, JP-A-2002-141115,
JP-A-2002-184476, JP-A-2002-356400, JP-A-2002-246623,
JP-A-2002-246624, JP-A-2002-261303, JP-A-2003-243053,
JP-A-2004-6235, JP-A-2003-323920, JP-A-2004-277197,
JP-A-2004-210605, JP-A-2005-135798, JP-A-2005-135799,
JP-A-2001-196105, JP-A-2002-100418, JP-A-2002-100419,
JP-A-2002-280084, JP-A-2003-272724, JP-A-2004-124124,
JP-A-9-237641, JP-A-11-273755, and JP-A-2004-247105.
[0184] The light-receiving electrode may be a tandem type electrode
so as to increase the utility ratio of the incident light, or the
like. Preferred examples of the tandem type construction include
those described in JP-A-2002-90989, JP-A-2002-222971,
JP-A-2003-168496, JP-A-2003-249275, JP-A-2005-166313,
JP-A-11-273753, JPA-2002-167808, JP-A-2005-129259,
JP-A-2002-231324, JP-A-2005-158620, JP-A-2005-158621,
JP-A-2005-191137 and JP-A-2003-333757.
[0185] The light-receiving electrode may be provided with the photo
management function by which light scattering and reflection are
efficiently achieved inside the light-receiving electrode layer.
Preferred examples thereof include those described in, for example,
JP-A-2002-93476, JP-A-2004-296373, JP-A-2002-352868,
JPA-2003-142170, JP-A-2003-59549, JP-A-2002-289274,
JP-A-2002-222968, JP-A-2003-217688, JP-A-2004-172110,
JP-A-2003-303629, JP-A-2004-343071, JP-A-2005-116302,
JP-A-09-259943, JP-A-10-255863, JP-A-2003-142171, JP-A-2002-110261,
and JP-A-2004-311197.
[0186] It is preferable to form a short circuit preventing layer
between the electrically conductive support and the porous
semiconductor fine particle layer, so as to prevent reverse current
due to a direct contact between the electrolyte liquid and the
electrode. Preferred examples thereof include those described in,
for example, JP-T-6-507999, JP-A-06-51113, JP-A-2000-178792,
JP-A-11-312541, JP-A-2000-285974, JP-A-2000-285979,
JP-A-2001-143771, JP-A-2001156314, JP-A-2001-307785,
JP-A-2002-151168, JP-A-2002-75471, JP-A-2003-163359,
JP-A-2003-163360, JP-A-2003-123856, WO 03/038909, JP-A-2002-289270,
JP-A-2002-319439, JP-A-2003-297443, JPA-2004-87622,
JP-A-2003-331934, JP-A-2003-243054, JP-A-2004-319130,
JP-A-2004-363069, JP-A-2005-71956, JP-A-2005-108807,
JP-A-2005-108836, and JP-A-2005-142087.
[0187] It is preferable to employ a spacer or a separator so as to
prevent the contact between the light-receiving electrode and the
counter electrode. Preferred examples thereof include those
described in, for example, JP-A-2001-283941, JP-A-2003-187883,
JP-A-2000-294306, JP-A-2002-175844, JP-A-2002-367686, and
JP-A-2004-253333.
[0188] According to the present invention, a photoelectric
conversion element having high conversion efficiency and a
photoelectrochemical cell can be produced at low cost.
EXAMPLES
[0189] The present invention will be described in more detail based
on the following examples, but the invention is not intended to be
limited thereto.
Synthesis Example 1
Preparation of Exemplified Dye D-1
[0190] The exemplified dye D-1 was prepared according to the method
shown in the following scheme 1.
##STR00021##
(i) Preparation of Compound D-1-b
[0191] Were stirred 112 g of methyl cyanoacetate and methyl
thioisocyanatoacetate in DMF in the presence of DBU for 2 hours at
0.degree. C., and then methyl bromoacetate was added thereto. The
mixture was stirred for 2 hours at 70.degree. C. The mixture was
extracted with ethyl acetate and concentrated, and was crystallized
from MeOH. Thus, 11.2 g of Compound D-1-b was obtained.
(ii) Preparation of Compound D-1-c
[0192] Compound D-1-b in an amount of 5 g was stirred in acetic
acid/hydrochloric acid=1/1, and was purified by column
chromatography. Thus, 0.4 g of Compound D-1-c was obtained.
(iii) Preparation of Compound D-1-d
[0193] Were dissolved 9.9 g of 4-iodophenol and 11.7 g of
1-iodohexane in 50 mL of DMAc (dimethylacetamide) under stirring at
room temperature, and 9.3 g of potassium carbonate was added
thereto. The mixture was stirred for 3.5 hours at room temperature.
Water and hexane were added thereto, and the mixture was
partitioned. The organic layer was concentrated and purified by
column chromatography. Thus, 12.8 g of
Compound D-1-d was obtained.
(iv) Preparation of Compound D-1-e
[0194] Were dissolved 3.5 g of indoline, 7.6 g of Compound D-1-d,
4.2 g of potassium carbonate, and 1.4 g of copper bromide in 10 mL
of sulfolane under stirring, and the solution was stirred for 3.5
hours at a set external temperature of 200.degree. C. The solution
was extracted from water with ethyl acetate, and the concentrate
was purified by column chromatography. Thus, 1.7 g of Compound
D-1-e was obtained.
(v) Preparation of Compound D-1-f
[0195] Was added 2 mL of phosphorus oxychloride to 6 mL of DMF
under ice cooling, and the mixture was stirred for 15 minutes.
Thereto 1.0 g of Compound D-1-b was added, and the mixture was
stirred for 3 hours at room temperature. Water was added to the
reaction liquid, and the mixture was stirred. A 10% aqueous
solution of sodium hydroxide was further added thereto, and the
mixture was stirred for one hour. The mixture was subjected to
extraction with ethyl acetate, concentration, and subsequent
recrystallization from MeOH. Thus, 0.98 g of Compound D-1-f was
obtained.
(vi) Preparation of Exemplified Dye D-1
[0196] Were dissolved 540 mg of Compound D-1-f and 380 mg of
Compound D-1-c in 25 mL of acetic acid under stirring at room
temperature. Thereto 158 mg of ammonium acetate was added, and the
mixture was heated and stirred at 90.degree. C. for 4 hours. The
mixture was cooled, and then water was added thereto. Precipitated
crystals were collected by filtration, and were recrystallized from
a MeOH/CH.sub.2Cl.sub.2 system. Thus, 420 mg of Exemplified Dye D-1
was obtained.
Synthesis Example 2
Preparation of Exemplified Dye D-3
[0197] Exemplified Dye D-3 was prepared according to the method
shown in the following scheme 2, with reference to the same method
as that used for Exemplified Dye D-1 and the descriptions in J. Am.
Chem. Soc., 2004, 126, 12218.
##STR00022##
(Synthesis of Other Example Dyes and Measurement of Maximum
Absorption Wavelength)
[0198] Exemplified Dyes D-2, D-7 and D-12 were synthesized in the
same manner as in the Synthesis Example 1.
[0199] The maximum absorption wavelengths of Exemplified Dyes D-1,
D-2, D-7 and D-12 were measured. The measurement was carried out by
dissolving each of the dyes in ethanol and using a
spectrophotometer (trade name: "U-4100", manufactured by Hitachi
High-Technologies Corp.). The results were 490 nm, 470 nm, 475 nm
and 516 nm for Exemplified Dyes D-1, D-2, D-7 and D-12,
respectively.
Example 1
[0200] A photoelectrochemical cell was produced according to the
method described below, and the cell was evaluated. The results are
presented in Table 1.
(1) Production of Transparent Electrically Conductive Support
[0201] Fluorine-doped tin dioxide was uniformly applied by a CVD
method over the entire surface of an alkali-free glass substrate
having a thickness of 1.9 mm, and thus a transparent electrically
conductive support coated on one side with a conductive tin dioxide
film having a thickness of 600 nm, a surface resistance of about 15
.OMEGA./cm.sup.2 and a light transmittance (500 nm) of 85%, was
formed.
(2) Preparation of Semiconductor Fine Particles
(i) Semiconductor Fine Particles a
[0202] A dispersion liquid of anatase type titanium dioxide
containing titanium dioxide at a concentration of 11% by mass was
synthesized according to the production method described in C. J.
Barbe et al., J. Am. Ceramic Soc., Vol. 80, p. 3157, using titanium
tetraisopropoxide as a titanium raw material and setting the
temperature of the polymerization reaction in an autoclave at
230.degree. C. The size of the primary particles of the obtained
titanium dioxide particles was 10 to 30 nm. The obtained dispersion
liquid was subjected to an ultracentrifuge to separate the
particles, and the aggregates were dried. Subsequently, the
aggregates were pulverized in an agate mortar, and thus
semiconductor fine particles a were obtained as white powder.
(ii) Semiconductor Fine Particles b
[0203] P-25 (trade name) manufactured by Nippon Aerosil Co., Ltd.
was used. P-25 is titanium oxide fine particles having a primary
particle size of 20 nm, a BET specific surface area of 50
m.sup.2/g, and an anatase content ratio of 77%, produced by a
method involving calcination in a gas phase.
(iii) Semiconductor Fine Particles c
[0204] Anatase type titanium oxide (anatase content ratio of 99%)
manufactured by Aldrich Company was used.
(3) Production of Porous Semiconductor Fine Particle Layer
[0205] The semiconductor fine particles a, b and c prepared above
were each added to 100 cc of a mixed solvent formed from water and
acetonitrile at a volume ratio of 4:1, at a concentration of 32 g
per 100 cc of the solvent, and the mixtures were uniformly
dispersed and mixed using a mixing conditioner of
rotation/revolution combination type. As a result, in the case of
the semiconductor fine particles a and b, the obtained white
semiconductor fine particle dispersion liquids became highly
viscous pastes having viscosities of 50 to 150 Ns/m.sup.2, and it
was found that these pastes had liquid properties adequate to be
used directly in the coating. However, in the case of the
semiconductor fine particles c, the semiconductor fine particle
dispersion liquid had a low viscosity, and a coating film having a
constant thickness could not be obtained. There, the dispersion
liquids obtained by using the semiconductor fine particles a and b
were each applied on the transparent electrically conductive
support coated with an electrically conductive tin dioxide film
produced above, using an applicator, and the dispersion liquid was
dried at room temperature for one hour. Thereby, a coating layer
having a uniform thickness of 40 to 70 .mu.m was formed. This
coating layer was further dried for 30 minutes at 120.degree. C.,
and then was exposed to UV light for 30 minutes from a mercury lamp
ultraviolet light source of 100 W, followed by a post-treatment. As
such, a porous semiconductor fine particle layer for dye
sensitization was produced. The final average thickness of the
porous semiconductor fine particle layer was 6.5 .mu.m for the
substrate a which used the semiconductor fine particles a, and 6.2
.mu.m for the substrate b which used the semiconductor fine
particles b.
[0206] In order to investigate the weight of the content of solids
excluding the semiconductor fine particles contained in the
dispersion liquid, the semiconductor fine particle layer was heated
in air at 350.degree. C. for 0.5 hours, and the weight change
before and after the heating was measured. As a result, the weight
decrease per unit area in sample Nos. 101 to 103, 104-1, 104-2,
104-3, 105 to 107 and 109, in which the dispersion liquids did not
contain any solids other than the semiconductor fine particle
layers a and b, was 0.3 mass % in all cases. In sample Nos. 108 and
110, the experiment was carried out using dispersion liquids
respectively containing 7.7 g and 11.7 g of a powder of
polyethylene glycol (PEG) having an average molecular weight of
500,000 per 100 cc of a solvent. The solids contents were 8.0 mass
% and 12.0 mass %, respectively.
(4) Preparation of Solution for Dye Adsorption
[0207] A comparative dye R-1 (dye described in Japanese Patent No.
4148374) described in Table 1 given below was dissolved in a mixed
solvent of dry acetonitrile:t-butanol:ethanol at a volume ratio of
2:1:1, to obtain a dye concentration of 3.times.10.sup.4
moles/liter. In this dye solution, an organic sulfonic acid
derivative having a structure of
p-C.sub.9H.sub.19--C.sub.6H.sub.4--O--(CH.sub.2CH.sub.2--O).sub.3--(CH.su-
b.2).sub.4--SO.sub.3Na was dissolved as an additive to obtain a
concentration of 0.025 moles/liter, and thus a solution for dye
adsorption was prepared.
[0208] Furthermore, the other dyes described in the Table 1 given
below each were dissolved in dry ethanol to obtain a concentration
of 3.times.10.sup.-4 moles/liter, and thus a solution for dye
adsorption was obtained.
(5) Adsorption of Dye
[0209] The substrates a and b each coated with a porous
semiconductor fine particle layer were immersed in the dye solution
for adsorption described above, and were left immersed under
stirring for 3 hours at 40.degree. C.
[0210] The dye was adsorbed to the semiconductor fine particle
layers as such, and thus dye-sensitized electrodes to be used in
photosensitive layers (photosensitive electrodes) were
produced.
(6) Production of Photoelectrochemical Cell
[0211] A dye-adsorbed porous semiconductor fine particle layer was
subjected to finishing, and thereby a circular photosensitive
electrode having a light-receiving area of 1.0 cm.sup.2 (diameter
about 1.1 cm) was formed. A platinum-deposited glass substrate as a
counter electrode was superposed against the photosensitive
electrode, with a frame type spacer (thickness 20 .mu.m) produced
from a thermally pressed polyethylene film inserted between the
electrodes. The spacer areas were `heated to 120.degree. C., and
the two substrates were pressed. Furthermore, the edge areas of the
cell were sealed with an epoxy resin adhesive. A room temperature
molten salt having formed from a composition of
1,2-dimethyl-3-propylimidazolium iodide/iodine=50:1 (mass ratio) as
an electrolyte liquid was introduced through a small hole for
electrolyte liquid injection preliminarily prepared at a corner
area of the substrate of the counter electrode, and was infiltrated
into the space between the electrodes from the small hole of the
substrate, by utilizing the capillary phenomenon. The process of
cell construction and the process of electrolyte liquid injection
described above were all carried out in dry air having a dew point
of -60.degree. C. as described above. After the injection of the
molten salt, the cell was suctioned in a vacuum for several hours,
and degassing of the inside of the cell containing the
photosensitive electrode and the molten salt was performed.
Finally, the small hole was sealed with low melting point glass.
Thereby, a photoelectrochemical cell in which an electrically
conductive support, a porous semiconductor fine particle electrode
adsorbed with a dye (photosensitive electrode), an electrolyte
liquid, a counter electrode and a support were laminated in this
sequence, was produced.
(7) Measurement of Photoelectric Conversion Efficiency
[0212] A xenon lamp of 500 W power (manufactured by Ushio, Inc.)
was mounted with a correction filter for sunlight simulation (trade
name: AM1.5 direct, manufactured by LOT-Oriel AG), and the
photoelectrochemical cell was irradiated with a pseudo-sunlight
having an incident light intensity of 100 mW/cm.sup.2, from the
side of the porous semiconductor fine particle electrode
(photosensitive electrode). The device was fixed closely on the
stage of a thermostat, and the temperature of the device during
irradiation was controlled to 50.degree. C. The
photocurrent-voltage characteristics were measured by scanning the
DC voltage applied to the device using a current voltage analyzer
(Source Measure Unit Model 238, manufactured by Keithley
Instruments, Inc.) at a constant rate of 10 mV/sec, and thereby
measuring the photocurrent outputted by the device. The energy
conversion efficiencies (.eta.) of the various devices mentioned
above determined thereby are described in Table 1, together with
the contents of the constituent elements of the cells
(semiconductor fine particles and sensitizing dye).
TABLE-US-00001 TABLE 1 Condition for producing photoelectrochemical
cell Content of solids excluding Cell performance Sample
Semiconductor semiconductor fine particles Conversion No. fine
particles Dye in coating liquid (mass %) efficiency (%) Remarks 101
a D-2 0.3 2.3 This invention 102 a D-3 0.3 2.4 This invention 103 a
D-7 0.3 2.4 This invention .sup. 104-1 a D-12 0.3 2.3 This
invention .sup. 104-2 a D-8 0.3 2.2 This invention .sup. 104-3 a
D-11 0.3 2.2 This invention 105 b D-2 0.3 2.2 This invention 106 b
D-3 0.3 2.1 This invention 107 b D-7 0.3 2.3 This invention 108 a
D-2 8.0 1.3 This invention 109 a R-1 0.3 1.2 Comparative example
110 a D-2 12.0 0.1 Comparative example
[0213] Comparative Dye R-1 (Compound Described in Japanese Patent
No. 4148374)
##STR00023##
[0214] From the results of Table 1, it was found that when a porous
semiconductor fine particle layer was produced by applying, on a
support, a particle dispersion liquid in which the content of
additives was 10 mass % or less of the dispersion liquid, and
heating the dispersion liquid coating, and the specific dye was
adsorbed thereto, a photoelectrochemical cell having higher
conversion efficiency could be obtained (sample Nos. 101 to 108),
as compared with the case where a comparative dye was adsorbed.
When a dispersion liquid having a content of solids excluding
semiconductor fine particles of 0.3 mass % was applied on a
support, and the dye for use in the present invention was adsorbed
thereto, a photoelectrochemical cell having particularly high
conversion efficiency could be obtained (sample Nos. 101 to
107).
[0215] On the other hand, when a comparative dye was adsorbed to
the porous semiconductor fine particles, the conversion efficiency
was lowered (sample No. 109).
[0216] Furthermore, when a dispersion liquid having a content of
solids excluding semiconductor fine particles of more than 10%, was
applied on the support, the conversion efficiency was extremely
lowered, even though the dye for use in the present invention was
adsorbed (sample No. 110).
Example 2
[0217] A photoelectrochemical cell was produced according to the
method described below, and the cell was evaluated. The results are
presented in Table 2.
(1) Production of Transparent Electrically Conductive Support
[0218] As a support for photosensitive electrode, a flexible
transparent electrically conductive support obtained by uniformly
applying a conductive thin film of tin oxide to a thickness of 200
nm, on one surface of a sheet having a thickness of 0.4 mm and
having the surfaces coated with fluorine, was used.
(2) Production of Conductive Sheet for Counter Electrode
[0219] A platinum film having a thickness of 300 nm was uniformly
coated by a vacuum sputtering method, on one surface of a Kapton
(registered trademark) film made of polyimide and having a
thickness of 0.4 mm. The surface resistance was 5
.OMEGA./cm.sup.2.
(3) Preparation of Semiconductor Fine Particle Dispersion
Liquid
[0220] A semiconductor fine particle dispersion liquid was prepared
in the same manner as in Example 1, using the semiconductor fine
particles a used in Example 1. In the sample Nos. 214 and 220, a
powder of polyethylene glycol (PEG) having an average molecular
weight of 500,000 was incorporated into the dispersion liquids in
amounts of 7.7 g and 11.7 g, respectively, per 100 cc of a solvent.
In the other semiconductor fine particle dispersion liquids, no
solids other than the semiconductor fine particles were added.
(4) Measurement of Solids in Semiconductor Fine Particle Dispersion
Liquid
[0221] Each of the dispersion liquids was applied to a thickness of
40 to 70 .mu.m, on an alkali-free glass substrate having a
thickness of 1.9 mm, using an applicator, and the dispersion liquid
coating was dried for one hour at room temperature. Subsequently,
the assembly was heated in air at 350.degree. C. for 0.5 hours, and
the weight change before and after the heating was measured. The
contents of solids excluding semiconductor fine particles of the
sample Nos. 214 and 220 were 8.0 mass % and 12.0 mass %,
respectively. The contents of solids excluding semiconductor fine
particles in the other samples were all 0.3 mass %.
(5) Preparation of Semiconductor Fine Particle Layer
[0222] The dispersion liquid prepared above was applied on the
transparent electrically conductive support prepared above, using
an applicator, and the dispersion liquid coating was dried one hour
at room temperature. Thereby, a uniform coating layer having a
thickness of 40 to 70 .mu.m was formed. This coating layer was
further treated under the conditions described in Table 2, and thus
a porous semiconductor fine particle layer for dye sensitization
was produced. The final average thickness of the porous
semiconductor fine particle layer was 6 to 7 .mu.m in all
cases.
(6) Adsorption of Dye
[0223] The support having a porous semiconductor fine particle
layer formed thereon was immersed in a dye solution for adsorption
prepared in the same manner as in Example 1, and the support was
left immersed under stirring for 3 hours at 40.degree. C.
[0224] The dye was adsorbed to the semiconductor fine particle
layer as such, and thereby a dye-sensitized electrode to be used in
a photosensitive layer (photosensitive electrode) was produced.
(7) Evaluation of Photoelectrochemical Cell
[0225] A photoelectrochemical cell was produced in the same manner
as in Example 1, using the dye-adsorbed semiconductor fine particle
electrode described above, and the photoelectric conversion
efficiency was measured. The results are presented in Table 2.
TABLE-US-00002 TABLE 2 Condition for producing cell Cell
Electrically Content of solids excluding Heat treatment performance
Sample Semiconductor conductive Sensitizing semiconductor fine
particles after coating/ Conversion No. fine particles support dye
in coating liquid (mass %) UV treatment efficiency (%) Remarks 201
a PEN D-2 0.3 120.degree. C. UV treatment 2.2 This invention 202 a
PEN D-3 0.3 120.degree. C. UV treatment 2.2 This invention 203 a
PET D-7 0.3 120.degree. C. UV treatment 2.1 This invention 204 a
PEN D-12 0.3 120.degree. C. UV treatment 2.1 This invention 205 a
PPS D-2 0.3 90.degree. C. UV treatment 1.5 This invention 206 a PC
D-3 0.3 90.degree. C. UV treatment 1.5 This invention 207 a PEN D-7
0.3 90.degree. C. UV treatment 1.6 This invention 208 a PEI D-2 0.3
150.degree. C. UV treatment 2.2 This invention 209 a PEN D-3 0.3
150.degree. C. UV treatment 2.3 This invention 210 a PEN D-7 0.3
150.degree. C. UV treatment 2.3 This invention 211 a PEN D-2 0.3
200.degree. C. UV treatment 1.5 This invention 212 a PEN D-3 0.3
200.degree. C. UV treatment 1.4 This invention 213 a PEN D-7 0.3
200.degree. C. UV treatment 1.3 This invention 214 a PEN D-2 8.0
120.degree. C. UV treatment 1.1 This invention 215 a PEN R-1 0.3
120.degree. C. UV treatment 0.6 Comparative example 216 a PEN R-1
0.3 90.degree. C. UV treatment 0.3 Comparative example 217 a PC R-1
0.3 150.degree. C. UV treatment 0.6 Comparative example 219 a PEN
R-1 0.3 200.degree. C. UV treatment 0.4 Comparative example 220 a
PEN D-2 12.0 120.degree. C. UV treatment 0.1 Comparative
example
[0226] As shown in Table 2, when a porous semiconductor fine
particle layer adsorbed with the specific dye was formed on a
support made of an electrically conductive polymer, an
electrochemical cell having a photoelectric conversion efficiency
of a practically useful level was obtained (sample Nos. 201 to
214). Particularly, when a porous semiconductor fine particle layer
was produced by applying, on a support, a dispersion liquid having
a content of solids excluding semiconductor fine particles of 0.3
mass %, conducting a heat treatment at 120 to 150.degree. C.,
subsequently irradiating the dispersion liquid coating with
ultraviolet radiation, and then adsorbing the specific dye thereto,
the photoelectric conversion efficiency was 2% or more (sample Nos.
201 to 204 and 208 to 210).
[0227] Furthermore, it was found that when a porous semiconductor
fine particle layer was produced by applying a dispersion liquid
having a solids content of 10% by mass or less on a support made of
an electrically conductive polymer and heating the dispersion
liquid coating, and the dye for use in the present invention was
adsorbed thereto, a photoelectrochemical cell having high
conversion efficiency was obtained, as compared with the case where
a comparative dye was adsorbed (comparison of sample Nos. 201 to
214 and sample Nos. 215 to 219). When a porous semiconductor fine
particle layer was used by applying a dispersion liquid having a
solids content of more than 10% by mass on a support made of an
electrically conductive polymer and heating the dispersion liquid
coating, even though the dye for use in the present invention was
adsorbed, the photoelectric conversion efficiency was decreased so
much to 0.1% (sample No. 220).
[0228] As discussed above, a dye-sensitized type photoelectric
conversion element can be produced at low cost by using a porous
semiconductor fine particle layer produced by the production method
of the present invention, as a photosensitive layer, without
necessitating a process of heating at high temperature.
Furthermore, a device having a performance useful even as a
photoelectrochemical cell can be provided with high conversion
efficiency, using a substrate excellent in flexibility, such as an
electrically conductive polymer.
[0229] Having described our invention as related to the present
embodiments, it is our intention that the invention not be limited
by any of the details of the description, unless otherwise
specified, but rather be construed broadly within its spirit and
scope as set out in the accompanying claims.
* * * * *